Michael Reid's box collection

Here are a number of boxes packed by congruent polycubes.

Box Collection
Michael Reid (reid@cflmath.com)
June 29, 2019

view in fixed-width font!


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Tricubes
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*
**


1x2x3 minimal
+--+--+--+
|  |     |
+  +--+  +
|     |  |
+--+--+--+

also: 1x5x9, 3x3x3


...............................................................................
Tetracubes
...............................................................................


*
***


1x2x4 minimal
+--+--+--+--+
|  |        |
+  +--+--+  +
|        |  |
+--+--+--+--+

also: 1x3x8, 2x2x6, 2x3x6, 3x3x4

...............................................................................

***
 *


1x4x4 minimal
+--+--+--+--+
|        |  |
+--+  +--+  +
|  |  |     |
+  +--+--+  +
|     |  |  |
+  +--+  +--+
|  |        |
+--+--+--+--+

also: 2x4x6, 2x4x9, 2x4x11, 2x5x12, 2x5x16, 2x5x20, 2x6x6, 2x7x8, 2x7x12,
      3x3x8, 3x4x6, 3x5x8, 5x5x8

...............................................................................

**
 **


2x3x4 minimal
+--+--+--+  +--+--+--+
|  |u    |  |    d|  |
+  +--+--+  +--+--+  +
|u |  |u |  | d|  | d|
+--+  +  +  +  +  +--+
|     |  |  |  |     |
+  +--+--+  +--+--+  +
|  |u    |  |    d|  |
+--+--+--+  +--+--+--+
level 1      level 2

also: 2x4x4, 2x4x5, 2x6x10, 6x6x6

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2*
*


2x2x2 minimal
+--+--+  +--+--+
|u    |  | d|  |
+  +--+  +--+  +
|  |u |  |    d|
+--+--+  +--+--+
level 1   level 2

also: 2x5x8, 2x5x12, 4x4x5 by Andrew Clarke
also: 4x5x6 by Andris Cibulis

...............................................................................

**
2


2x2x2 minimal
+--+--+  +--+--+
|     |  |     |
+  +--+  +--+  +
|u |u |  | d| d|
+--+--+  +--+--+
level 1   level 2

also: 2x3x8, 2x3x12, 2x4x9, 2x5x6, 2x5x10, 3x4x9, 3x4x10, 3x4x11, 3x4x13,
      3x4x14, 3x4x15, 3x5x8, 3x5x12, 3x6x6, 3x6x10, 4x4x5, 4x5x5, 4x5x7, 4x7x7


allowing reflections:
also: 2x3x4, 2x3x6, 3x3x4


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Pentacubes
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*
****


1x2x5 minimal
+--+--+--+--+--+
|  |           |
+  +--+--+--+  +
|           |  |
+--+--+--+--+--+

also: 1x7x15, 3x5x5

...............................................................................

**
***


1x2x5 minimal
+--+--+--+--+--+
|     |        |
+     +--+     +
|        |     |
+--+--+--+--+--+

also: 1x7x15, 3x3x5

...............................................................................

 *
****


1x5x10 minimal by David Klarner
+--+--+--+--+--+--+--+--+--+--+
|  |           |  |           |
+  +--+--+  +--+  +--+--+  +--+
|     |  |  |           |  |  |
+  +--+  +--+--+--+--+--+--+  +
|  |           |           |  |
+  +--+--+--+--+--+--+  +--+  +
|  |  |           |  |  |     |
+--+  +--+--+  +--+  +--+--+  +
|           |  |           |  |
+--+--+--+--+--+--+--+--+--+--+


also: 1x9x20, 1x9x30, 1x9x45, 1x9x55, 1x10x14, 1x10x16, 1x10x23, 1x10x27,
       1x11x20, 1x11x30, 1x11x35, 1x11x45, 1x12x50, 1x12x55, 1x12x60, 1x12x65,
       1x12x70, 1x12x75, 1x12x80, 1x12x85, 1x12x90, 1x12x95, 1x13x20, 1x13x30,
       1x13x35, 1x13x45, 1x14x15, 1x15x15, 1x15x16, 1x15x17, 1x15x19, 1x15x21,
       1x15x22, 1x15x23, 1x17x20, 1x17x25, 1x18x25, 1x18x35, 1x22x25
also: 2x4x10, 2x4x15, 2x5x6, 2x5x8, 2x5x11, 2x5x13, 2x5x15, 2x7x10, 2x7x15,
      3x4x5, 3x5x9, 3x5x11, 3x6x10, 3x6x15, 3x7x10, 3x7x15,
      4x4x5, 4x5x5,
      5x5x5, 5x5x6, 5x5x7, 5x7x7

...............................................................................

* *
***


   +--+        +--+
   |u |        | d|
+--+--+--+  +--+  +--+
|u     u |  | d|  | d|
+--+--+--+  +--+  +--+
   |u |        | d|
   +--+        +--+
level 1      level 2


2x3x5 minimal
+--+--+--+--+--+
|     |  |     |
+  +--+  +--+  +
|  |        |  |
+  +--+  +--+  +
|     |  |     |
+--+--+--+--+--+
(2 levels deep)

also: 2x10x10, 2x10x14, 2x11x20, 2x11x25, 3x3x10, 3x5x7, 4x4x5, 4x5x5, 5x5x11

...............................................................................

 ***
**


2x4x5 minimal
+--+--+--+--+--+  +--+--+--+--+--+
|   u |        |  |  | d      |  |
+--+--+  +--+--+  +  +--+--+--+  +
|u |     |     |  | d|        |  |
+  +--+--+  +--+  +--+  +--+--+  +
|  |        |u |  |     |     | d|
+  +--+--+--+  +  +--+--+  +--+--+
|  |      u |  |  |        | d   |
+--+--+--+--+--+  +--+--+--+--+--+
level 1            level 2

also: 2x5x5, 2x5x6, 2x5x7, 3x4x10, 3x4x15, 3x5x8, 3x5x12, 3x5x13, 3x5x14, 3x5x15,
      3x5x17, 3x5x18, 3x5x19, 3x6x10, 3x6x15, 3x7x10, 3x7x15, 3x9x10, 5x5x5

...............................................................................

*
*
***


+--+--+     +--+--+     +--+--+     +--+--+     +--+--+     +--+--+
|u |u |     |ud|ud|     | d| d|     |u |u |     |ud|ud|     | d| d|
+  +  +     +--+--+     +--+--+     +--+--+     +--+--+     +  +  +
|  |  |     |u |u |     |ud|ud|     | d| d|     |  |  |     |  |  |
+  +  +--+  +  +  +--+  +--+--+--+  +--+--+--+  +  +  +--+  +  +  +--+
|  |  |u |  |  |  |ud|  |       d|  |      u |  |  |  |ud|  |  |  | d|
+--+--+--+  +  +  +--+  +--+--+--+  +--+--+--+  +  +  +--+  +--+--+--+
|      u |  |  |  |ud|  |u |u | d|  |ud|ud|u |  | d| d|ud|  |       d|
+--+--+--+  +--+--+--+  +--+--+--+  +--+--+--+  +--+--+--+  +--+--+--+
level 1      level 2     level 3     level 4     level 5     level 6


3x5x6 minimal
+--+--+--+
|        |
+--+--+  +
|     |  |
+     +  +
|     |  |
+     +--+
|        |
+        +
|        |
+--+--+--+
(6 levels deep)


also: 3x5x8, 3x7x20, 3x7x25, 3x7x30, 3x7x35, 3x9x10, 3x9x15,
       3x10x10, 3x10x11, 3x10x13, 3x11x15, 3x13x15,
      4x4x10, 4x4x15, 4x5x6, 4x5x7, 4x5x8, 4x5x9, 4x5x10, 4x5x11,
      5x5x6, 5x5x9, 5x5x10, 5x5x11, 5x5x13, 5x5x14, 5x7x7, 5x7x9

...............................................................................

***
 *
 *


3x10x10 co-minimal by Frits Go"bel
+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+
|x |x |x |  |  |x |        |x |  |x |x |x |      x |  |      x |
+--+--+--+  +  +--+--+  +--+--+  +  +  +  +--+--+--+  +--+--+--+
|  |        |        |  |  |x |  |  |  |  |        |  |      x |
+  +--+--+  +  +--+--+  +  +--+  +  +  +  +--+  +--+  +--+--+--+
|        |  |  |  |x |  |  |x |  |  |  |  |  |  |  |x |      x |
+  +--+--+--+--+  +--+--+  +--+  +--+--+--+  +  +  +--+--+--+--+
|  |  |x |        |  |        |  |      x |  |  |        |  |  |
+--+  +--+--+--+  +  +--+--+--+  +--+--+--+  +--+  +--+--+  +  +
|x |  |        |  |  |        |  |x |  |        |  |        |  |
+--+  +--+  +--+--+  +--+  +--+  +  +  +--+--+--+--+--+--+  +  +
|        |  |  |        |  |x |  |  |        |  |        |  |x |
+--+--+--+  +  +--+--+--+  +--+  +  +  +--+--+  +--+  +--+--+--+
|        |  |        |x |  |  |  |  |  |        |  |  |x       |
+--+  +--+--+  +--+--+--+--+  +  +--+--+--+--+  +  +  +--+--+--+
|x |  |  |x |  |  |  |        |  |x       |x |  |  |  |  |  |  |
+--+  +  +--+--+  +  +--+--+  +  +--+--+--+  +--+  +--+  +  +  +
|x |  |  |        |        |  |  |x       |  |        |  |  |  |
+--+--+  +--+--+  +  +--+--+--+  +--+--+--+  +--+--+--+  +  +  +
|x |        |x |  |  |x |x |x |  |x       |  |x       |x |x |x |
+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+
levels 1, 3                       level 2


5x5x12 co-minimal by Michael Beeler
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
|   u    |  |u |  |  |ud|      ud|  |u | d|  |u | d|  |ud      |ud|  |  | d|  |    d   |
+--+--+--+  +--+  +  +--+--+--+--+  +--+--+  +--+--+  +--+--+--+--+  +  +--+  +--+--+--+
|   u    |  |u |  |  |ud|      ud|  |u | d|  |u | d|  |ud      |ud|  |  | d|  |    d   |
+--+--+--+  +--+  +  +--+--+--+--+  +--+--+  +--+--+  +--+--+--+--+  +  +--+  +--+--+--+
|u |  |        |  |ud|u |u |u |  |  | d|ud|ud|ud|u |  |  | d| d| d|ud|  |        |  | d|
+--+  +--+--+--+  +--+--+--+--+  +  +--+  +--+  +--+  +  +--+--+--+--+  +--+--+--+  +--+
|u |  |        |  |ud      |  |  |  | d|  |  |  |u |  |  |  |      ud|  |        |  | d|
+--+  +--+  +--+  +--+--+--+  +  +  +--+  +  +  +--+  +  +  +--+--+--+  +--+  +--+  +--+
|        |  |u |  |  |        |ud|  |u |  |  |  | d|  |ud|        |  |  | d|  |        |
+--+--+--+  +--+  +  +--+--+  +--+  +--+--+  +--+--+  +--+  +--+--+  +  +--+  +--+--+--+
|   u    |  |u |  |  |ud|u |  |ud|  |u | d|ud|u | d|  |ud|  | d|ud|  |  | d|  |    d   |
+--+--+--+--+--+  +  +--+--+--+  +  +--+--+--+--+--+  +  +--+--+--+  +  +--+--+--+--+--+
|u |  |   u    |  |ud|  |u |ud|  |  | d|u |ud| d|u |  |  |ud| d|  |ud|  |    d   |  | d|
+--+  +--+--+--+  +--+  +--+--+  +  +--+--+  +--+--+  +  +--+--+  +--+  +--+--+--+  +--+
|u |  |        |  |ud|        |  |  | d|  |  |  |u |  |  |        |ud|  |        |  | d|
+--+  +--+  +--+  +  +  +--+--+--+  +--+  +  +  +--+  +--+--+--+  +  +  +--+  +--+  +--+
|        |  |u |  |  |  |      ud|  |u |  |  |  | d|  |ud      |  |  |  | d|  |        |
+--+--+--+  +--+  +  +--+--+--+--+  +--+  +--+  +--+  +--+--+--+--+  +  +--+  +--+--+--+
|        |  |u |  |  |u |u |u |ud|  |u |ud|ud|ud| d|  |ud| d| d| d|  |  | d|  |        |
+--+  +--+--+--+  +--+--+--+--+  +  +--+--+  +--+--+  +  +--+--+--+--+  +--+--+--+  +--+
|u |  |   u    |  |ud      |ud|  |  | d|u |  | d|u |  |  |ud|      ud|  |    d   |  | d|
+--+  +--+--+--+  +--+--+--+--+  +  +--+--+  +--+--+  +  +--+--+--+--+  +--+--+--+  +--+
|u |  |   u    |  |ud      |ud|  |  | d|u |  | d|u |  |  |ud|      ud|  |    d   |  | d|
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
level 1            level 2           level 3           level 4           level 5

also: 3x7x20, 3x8x15, 3x8x35, 3x8x40, ...
also: 8x8x10, 8x8x25
also: 8x10x10, 10x10x10 by George Sicherman

...............................................................................

 **
**
 *


3x6x10 co-minimal by Patrick Hamlyn
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|  |u |   u |     |  |   ud|  |ud   |u |  |  | d   | d|  | d|
+  +--+--+--+  +--+  +--+--+  +--+--+  +  +  +--+--+--+  +--+
|        |     |u |  |  |        |  | d|  |        |        |
+--+  +--+--+  +--+  +  +--+--+  +  +  +  +--+  +--+--+--+  +
|u |  |u    |  |  |  |ud|   ud|  |u |  |  | d|  | d|  | d|  |
+  +--+--+--+--+  +  +--+--+--+--+  +--+  +--+--+--+  +--+--+
|  |u |  |  |u |u |  |  |ud   |  | d|ud|  |    d|        | d|
+--+--+  +  +--+--+  +  +--+--+  +--+  +  +--+--+--+--+  +--+
|u |     |        |  |ud|  |        |  |  | d|  |     |  |  |
+  +--+  +--+  +--+  +--+  +--+--+  +--+  +--+  +--+  +--+  +
|  |  |     |  |u |  |  |        |  |ud|  |        |     | d|
+--+  +--+--+--+--+  +  +--+  +--+--+  +  +--+--+  +  +--+--+
|u |        |u    |  |ud|u |  |   ud|  |  | d| d|  |  | d|  |
+--+--+  +--+--+--+  +--+  +--+--+--+--+  +  +--+--+--+--+  +
|  |u |  |u |  |u |  |  | d|  |ud   |ud|  |  |  |    d|  | d|
+  +--+--+--+  +--+  +  +  +  +--+--+  +  +--+  +--+--+  +--+
|        |        |  |u |  |        |  |  | d|     |        |
+--+  +--+--+--+  +  +  +--+--+  +--+--+  +--+  +--+--+--+  +
|u |  |u |   u |  |  | d|   ud|  |ud   |  |     | d   | d|  |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3


5x6x6 co-minimal by Torsten Sillke and Keiichiro Ishino (independently)
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|     |u    |u |  |  |  |   ud|    d u |  |u |  | d|u |  | d|  | d u    |ud   |  |  |  | d|    d|     |
+--+  +--+--+--+  +  +  +--+--+--+--+--+  +--+  +--+--+  +--+  +--+--+--+--+--+  +  +  +--+--+--+  +--+
|u |     |u |  |u |  | d|u |u   d   |ud|  |u | d| d|u |u | d|  |ud|   u   d| d|u |  | d|  | d|     | d|
+--+  +--+--+  +--+  +  +--+--+--+--+  +  +--+  +--+--+  +--+  +  +--+--+--+--+  +  +--+  +--+--+  +--+
|  |  |u |        |  |u |    d u |u |  |  | d|u |u | d| d|u |  |  | d| d u    | d|  |        | d|  |  |
+  +--+--+--+--+  +  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +  +--+--+--+--+  +
|        |u |  |  |  |  |u |u   d   |u |  |u | d| d|u |u | d|  | d|   u   d| d|  |  |  |  | d|        |
+--+  +--+--+  +--+  +  +--+--+--+--+  +  +--+  +--+--+  +--+  +  +--+--+--+--+  +  +--+  +--+--+  +--+
|u |  |u |     |u |  |ud|    d u |u | d|  | d|u |u | d| d|u |  |u | d| d u    |ud|  | d|     | d|  | d|
+  +--+--+--+  +--+  +--+--+--+--+--+  +  +--+  +--+--+  +--+  +  +--+--+--+--+--+  +--+  +--+--+--+  +
|  |u |   u |     |  |u   d   |ud   |  |  | d|  |u | d|  |u |  |  |   ud|   u   d|  |     | d   | d|  |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4              level 5

also: 3x6x15, 3x7x10, 3x7x15, 3x8x10, ...

...............................................................................

*
**
 **


5x6x6 by Torsten Sillke  (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|   u |   u |     |  |  | d u | d u |  |  |  |u | d|u | d|  |  |  | d u | d u |  |  |     | d   | d   |
+--+--+--+--+  +--+  +  +--+--+--+--+  +  +  +--+--+--+--+  +  +  +--+--+--+--+  +  +--+  +--+--+--+--+
|  |   u |     |  |  |     | d u |     |  |     |u | d|     |  |     | d u |     |  |  |     | d   |  |
+  +--+--+  +--+  +  +--+  +--+--+  +--+  +--+  +--+--+  +--+  +--+  +--+--+  +--+  +  +--+  +--+--+  +
|u |     |  |     |  | d|     |     |u |  |u |     |     | d|  | d|     |     |u |  |     |  |     | d|
+--+  +--+--+  +--+  +  +--+--+--+--+  +  +--+--+--+--+--+--+  +  +--+--+--+--+  +  +--+  +--+--+  +--+
|     |  |     |u |  |u |     |     | d|  | d|     |     |u |  |u |     |     | d|  | d|     |  |     |
+  +--+  +--+--+  +  +--+  +--+--+  +--+  +--+  +--+--+  +--+  +--+  +--+--+  +--+  +  +--+--+  +--+  +
|  |     |u    |  |  |     |u   d|     |  |     | d|u |     |  |     |u   d|     |  |  |    d|     |  |
+--+  +--+--+--+--+  +  +--+--+--+--+  +  +  +--+--+--+--+  +  +  +--+--+--+--+  +  +--+--+--+--+  +--+
|     |u    |u    |  |  |u   d|u   d|  |  |  | d|u | d|u |  |  |  |u   d|u   d|  |  |    d|    d|     |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4              level 5

also: 3x7x20, 3x7x25, 3x7x30, 3x7x35, ...
also: 5x7x9 by Patrick Hamlyn

...............................................................................

**
 *
 **


6x10x10 minimal by Yoshiya "Wolf" Shindo
+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+
|  |     |  |u |     |  |u    |  |     |u      d|u |u    |ud|  |  |     | d|u    | d|ud|    d|  |
+  +  +--+  +--+--+  +  +--+--+  +--+  +--+--+--+--+--+--+--+  +  +--+  +--+--+--+  +--+--+--+  +
|u |  |u |        |  |        |  |ud|  | d    u |   u |        |  | d|  |   u | d|  |ud|        |
+--+  +--+--+--+  +  +--+--+  +  +--+  +--+--+--+--+--+  +--+--+  +  +  +--+--+--+  +--+  +--+--+
|     |  |  |u |  |     |u |  |  |  |     |  | d    u |  | d|u |  |  |     |  |u |u | d|  |  | d|
+--+--+  +  +--+--+--+--+--+--+  +  +--+--+  +--+--+--+--+  +  +  +--+--+--+  +--+--+--+--+  +--+
|        |        |     |     |  |u |u |u |        |     |  |  |  |ud|ud| d|        |     |u |u |
+  +--+--+--+--+  +  +--+  +--+  +--+  +  +--+--+  +  +--+  +  +  +--+--+--+--+--+  +  +--+--+  +
|  |     |     |  |  |u |  |u |  |u |  |  |     |  |  | d|u | d|  | d    u |     |  |  |u | d|  |
+--+  +--+  +--+--+  +--+  +--+  +--+--+  +  +--+--+  +  +--+--+  +--+--+--+  +--+--+  +--+--+--+
|u |  |u |  |  |     |     |  |  | d|u | d|  |  |     |  |  |u |  |  | d|u |  |  |     |u      d|
+--+  +--+  +  +--+--+--+--+  +  +  +  +--+  +  +--+--+  +  +--+  +  +--+--+  +  +--+--+--+--+--+
|     |     |        |        |  |  |  |     |        |u |u |u |  |u |u |     |        | d|ud|ud|
+--+--+--+--+--+--+  +  +--+--+  +  +  +--+--+--+--+  +--+--+  +  +--+  +--+--+--+--+  +--+--+--+
|  |u |     |  |u |  |  |     |  |u | d|  |u      d|  |     |  |  | d|  |  | d|u |u |  |     |  |
+  +--+--+  +  +--+--+--+  +--+  +--+--+  +--+--+--+--+--+  +--+  +--+--+  +--+  +--+--+--+  +  +
|        |  |        |u |  |u |  |        |u    |u      d|  |ud|  |        |ud|  | d|u    |  | d|
+--+--+  +  +--+--+  +--+  +  +  +  +--+--+--+--+--+--+--+  +--+  +  +--+--+--+  +--+--+--+  +--+
|   u |  |     |u |  |     |  |  |  |ud|   u |u | d    u |     |  |  | d   |ud| d|   u | d|     |
+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+
level 1                           level 2                          level 3

+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+
|  |u    |ud|u |    d|u |     |  |  |ud|    d| d|u      d|     |  |    d|  |     | d|  |     |  |
+  +--+--+--+  +--+--+--+  +--+  +  +--+--+--+--+--+--+--+  +--+  +--+--+  +  +--+--+  +--+  +  +
|        |ud|  |u | d   |  |u |  |        | d   | d    u |  |ud|  |        |  |        | d|  | d|
+--+--+  +--+  +--+--+--+  +  +  +--+--+  +--+--+--+--+--+  +--+  +  +--+--+  +  +--+--+--+  +--+
|u |  |  |u | d| d|  |     |  |  | d|u |  | d    u |  |     |  |  |  | d|     |  | d|  |  |     |
+--+  +--+--+--+--+  +--+--+--+  +  +  +--+--+--+--+  +--+--+  +  +--+--+--+--+--+--+  +  +--+--+
| d| d|     |        |u |ud|ud|  |  |  |     |        | d| d| d|  |     |     |        |        |
+  +--+--+  +  +--+--+--+--+--+  +  +  +--+  +  +--+--+  +  +--+  +--+  +--+  +  +--+--+--+--+  +
|  |u | d|  |  |     | d    u |  |u | d|u |  |  |     |  |  | d|  | d|  | d|  |  |     |     |  |
+--+--+--+  +--+--+  +--+--+--+  +--+--+  +  +--+--+  +  +--+--+  +--+  +--+  +--+--+  +--+  +--+
|u      d|     |  |  | d|u |  |  | d|  |  |     |  |  |u | d|u |  |  |     |     |  |  | d|  | d|
+--+--+--+--+--+  +  +--+--+  +  +--+  +  +--+--+  +  +--+  +  +  +  +--+--+--+--+  +  +--+  +--+
|ud|ud|u |        |     | d| d|  | d| d| d|        |     |  |  |  |        |        |     |     |
+--+--+--+  +--+--+--+--+  +--+  +  +--+--+  +--+--+--+--+  +  +  +--+--+  +  +--+--+--+--+--+--+
|  |     |  | d| d|u |  |  |u |  |  |     |  |u      d|  |u | d|  |     |  |  | d|  |     | d|  |
+  +  +--+--+--+  +--+  +--+--+  +--+  +--+--+--+--+--+  +--+--+  +--+  +--+--+--+  +  +--+--+  +
|u |  |    d|u |  |ud|        |  |ud|  |u      d|    d|        |  | d|  | d|        |  |        |
+--+  +--+--+--+  +--+--+--+  +  +--+  +--+--+--+--+--+--+--+  +  +  +  +--+  +--+--+  +  +--+--+
|     |u | d   |u |ud|   u |  |  |     | d    u | d| d   |ud|  |  |  |     |  | d|     |  | d   |
+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+
level 4                           level 5                          level 6

also: 4x10x50, 5x8x20, 5x9x15
also: 6x6x25 by Yoshiya "Wolf" Shindo
also: 10x10x10 by George Sicherman

...............................................................................

 **
2*


2x2x5 minimal
+--+--+--+--+--+  +--+--+--+--+--+
|u |     |   u |  | d   |     | d|
+--+  +--+  +--+  +--+  +--+  +--+
|u    |     |u |  | d|     |    d|
+--+--+--+--+--+  +--+--+--+--+--+
level 1            level 2

also: 2x5x13, 3x4x10, 3x4x15, 3x6x10, 3x6x15, 3x7x10, 3x7x25, 3x9x10,
      3x9x15, 3x11x15, 4x5x5, 5x5x6, 5x5x9, 5x5x11, 5x7x7, 5x7x9

allowing reflections:
also: 2x5x5, 3x5x8, 3x5x12

...............................................................................

 *
2**


2x2x5 minimal
+--+--+--+--+--+  +--+--+--+--+--+
|u |  |      u |  | d      |  | d|
+--+  +--+  +--+  +--+  +--+  +--+
|u       |  |u |  | d|  |       d|
+--+--+--+--+--+  +--+--+--+--+--+
level 1            level 2

also: 2x7x15, 3x4x10, 3x4x15, 3x5x6, 3x5x8, 3x5x9, 3x5x10, 3x5x11, 3x5x13,
      3x7x10, 3x7x15, 4x5x5, 5x5x5, 5x5x7, 5x7x7

allowing reflections:
also: 2x3x10, 2x3x15, 2x5x7, 3x3x10, 3x3x15, 3x4x5, 3x5x5, 3x5x7

...............................................................................

2*
**


+--+--+     +--+--+
|u    |     | d|  |
+  +--+--+  +  +  +--+
|u |u  u |  | d| d  d|
+--+--+--+  +--+--+--+
level 1      level 2


2x2x5 minimal
+--+--+--+--+--+
|     |        |
+     +--+     +
|        |     |
+--+--+--+--+--+
(2 levels deep)

also: 2x3x5, 3x7x25, 3x9x15, 5x5x9, 5x7x7

...............................................................................

  2
***


+--+--+--+  +--+--+--+
|        |  |        |
+  +--+--+  +--+--+  +
|u |  |u |  | d|  | d|
+--+  +--+  +--+  +--+
level 1      level 2


   +--+     +--+        +--+     +--+
   |u |     |u |        | d|     | d|
+--+--+--+--+  +--+  +--+  +--+--+--+--+
|u    |        |u |  | d|        |    d|
+--+  +--+--+--+--+  +--+--+--+--+  +--+
|u |  |  |      u |  | d      |  |  | d|
+  +  +  +--+--+--+  +--+--+--+  +  +  +
|  |  |u |u       |  |       d| d|  |  |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2


2x5x6 co-minimal
+--+--+--+--+--+--+
|        |        |
+  +--+  +  +--+  +
|  |  |  |  |  |  |
+--+  +--+--+  +--+
|                 |
+                 +
|                 |
+                 +
|                 |
+--+--+--+--+--+--+
(2 levels deep)


3x4x5 co-minimal
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
|     |        |  |      u |   u |  |     | d|  | d|
+  +--+  +--+--+  +--+--+--+--+--+  +--+  +  +  +  +
|u |u |u |u |  |  |ud|ud| d| d   |  | d| d|  |  |  |
+--+--+--+  +  +  +--+--+--+--+--+  +--+--+--+  +  +
|u |u |  |  |  |  |ud|ud|u |u    |  | d| d| d| d|  |
+--+  +  +  +  +  +--+--+--+--+--+  +  +--+  +--+--+
|     |u |  |u |  |       d|    d|  |     |        |
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
level 1            level 2           level 3


also: 2x4x10, 2x4x15, 2x5x10, 2x5x14, 2x5x15, 2x5x17, 2x5x19, 2x7x10, 2x7x15,
      3x3x10, 3x3x15, 3x5x5, 3x5x6, 3x5x7,
      4x4x5, 4x5x5,
      5x5x5


same pentacube, allowing reflections


+--+--+     +--+--+     +--+--+
|u |u |     | d|ud|     |  | d|
+  +--+--+  +--+--+--+  +  +  +--+
|        |  |u       |  | d|     |
+--+--+--+  +--+--+--+  +--+--+--+
level 1      level 2     level 3


2x3x5 minimal
+--+--+--+--+--+
|     |        |
+     +--+     +
|        |     |
+--+--+--+--+--+
(3 levels deep)

also: 2x4x5, 2x5x5, 3x3x5

...............................................................................

 2
***


2x5x5 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+  +--+--+--+--+--+
|   u    |u |  |  |  | d|    d   |
+--+--+--+  +  +  +  +  +--+--+--+
|u    |  |  |u |  | d|  |  |    d|
+--+--+  +--+  +  +  +--+  +--+--+
|  |u |   u |  |  |  | d   | d|  |
+  +--+  +--+--+  +--+--+  +--+  +
|u |  |  |   u |  | d   |  |  | d|
+  +  +--+--+--+  +--+--+--+  +  +
|  |u |   u    |  |    d   | d|  |
+--+--+--+--+--+  +--+--+--+--+--+
level 1            level 2

also: 2x5x8, 2x5x11, 2x5x14, 2x5x17, 2x12x20, 2x12x25, ...

...............................................................................

2**
*


3x5x6 minimal by Patrick Hamlyn
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u    |u       |u |  |ud|  | d|u |  |ud|  | d|       d|    d|
+  +--+  +--+--+--+  +--+  +--+--+  +--+  +--+--+--+  +--+  +
|  |  |  |      u |  |u |  |      u | d|  | d      |  | d|  |
+--+  +--+--+--+  +  +--+  +--+--+--+--+  +  +--+--+--+--+--+
|  |  |   u |  |  |  |   u |  | d|u |  |  |  | d|       d|  |
+  +  +--+  +  +--+  +--+--+  +--+--+  +  +--+--+--+--+  +  +
|  |u    |  |  |u |  |u | d|  |       d|  | d      |  |  |  |
+  +--+--+  +  +--+  +--+--+  +--+--+--+  +  +--+--+  +--+  +
|u    |u |  |u    |  | d|    d|u | d|u |  |  |       d|    d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3

also: 2x8x10, 2x9x15, 2x10x10, 2x10x12, 2x10x14, 2x11x30, 2x12x15, 2x13x30, 2x15x15,
      3x4x30, 3x4x45, 3x5x9, 3x7x15, 3x8x15, 4x4x10, 4x5x6, 5x5x6

...............................................................................

**2
*


4x5x6 minimal by Patrick Hamlyn
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
|      u |u |u |  |u    | d| d|ud|  |ud|u |u |    d|  | d| d| d      |
+  +--+--+  +  +  +--+--+--+--+--+  +--+--+--+--+--+  +  +  +--+--+  +
|  |u |  |  |  |  |u | d|      u |  | d      |u | d|  |  |  |  | d|  |
+--+--+  +  +--+  +--+  +  +--+--+  +--+--+  +  +--+  +--+  +  +--+--+
|u       |     |  | d|  |  |     |  |     |  |  |u |  |     |       d|
+--+--+--+--+--+  +--+  +--+  +--+  +--+  +--+  +--+  +--+--+--+--+--+
|     |      u |  |     |  |  | d|  |u |  |  |     |  | d      |     |
+--+  +  +--+--+  +--+--+  +  +--+  +--+  +  +--+--+  +--+--+  +  +--+
|  |  |  |u |  |  |u       | d|u |  | d|u |       d|  |  | d|  |  |  |
+  +  +--+--+  +  +--+--+--+--+--+  +--+--+--+--+--+  +  +--+--+  +  +
|u |u |u       |  |ud| d| d|   u |  | d   |u |u |ud|  |       d| d| d|
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
level 1            level 2           level 3           level 4


also: 4x8x20, 4x8x130, 4x10x10, 5x6x29, 5x6x46, 5x6x47, 5x7x24, 5x7x30, 5x10x18,
      6x6x15, 6x6x20, 6x6x25, 6x7x10, 6x7x15, 6x9x10, 6x9x15
also: 6x10x10 by George Sicherman


same pentacube, allowing reflections


3x5x6 minimal by Patrick Hamlyn
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u    |u |      u |  |ud|u | d      | d|  | d| d      |     |
+--+--+--+  +--+--+  +--+--+--+--+  +--+  +  +--+--+  +  +--+
|u       |  |   u |  | d|u       |  |ud|  |  | d|  |  |  | d|
+--+--+  +--+--+--+  +--+--+--+  +--+--+  +--+--+  +--+  +  +
|  |u |  |      u |  |u | d|  |  |u | d|  | d      |  | d|  |
+  +  +--+  +--+--+  +--+--+  +--+--+--+  +--+--+--+  +--+--+
|u |  |  |  |u |  |  |ud|  |       d|u |  | d   |  |       d|
+--+  +  +--+--+  +  +--+  +--+--+--+--+  +--+--+  +--+--+--+
|     |      u |u |  |u |      u | d|ud|  | d      | d|    d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3

also: 3x4x15, 3x5x9, 3x7x15, 4x4x10, 5x5x6

...............................................................................

 **
*2


4x8x10 co-minimal
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|   u |  |   u |   u |  |  |  | d   |  | d   | d   |  |   u |   u |  |   u |  |  |  | d   | d   |  | d   |
+--+--+  +--+  +--+  +  +  +  +  +--+  +--+--+--+--+  +--+--+--+--+  +--+  +  +  +  +  +--+  +--+  +--+--+
|u    |u    |  |  |  |u |  | d|  | d|u |u    |    d|  |u    |    d| d|u |  |u |  | d|  |  |  |    d|    d|
+  +--+--+  +--+  +--+--+  +--+--+--+--+  +--+--+  +  +  +--+--+  +--+--+--+--+  +--+--+  +--+  +--+--+  +
|  |   u |  |   u |u    |  |  |  | d   |  | d| d|  |  |  |u |u |  |   u |  |  |  |    d| d   |  | d   |  |
+--+--+  +--+--+--+  +--+  +  +  +--+--+--+  +--+--+  +--+--+  +--+--+--+  +  +  +--+  +--+--+--+  +--+--+
|u    |  |u    |     |  |  | d|u |  | d|  |  |u    |  |    d|  |  |u |  | d|u |  |  |     |    d|  |    d|
+  +--+--+  +--+--+--+  +  +--+--+  +--+  +--+  +--+  +--+  +--+  +--+  +--+--+  +  +--+--+--+  +--+--+  +
|  |u |     |u    |   u |  |  | d u |    d|u |  | d|  |u |  | d|u    | d u |  |  | d   |    d|     | d|  |
+--+--+--+--+--+--+--+--+  +  +--+--+--+--+--+--+  +  +  +--+--+--+--+--+--+  +  +--+--+--+--+--+--+--+--+
|u    |   u |     |u |  |  | d|  |u | d   |u   d|  |  |  |u   d|   u | d|  |u |  |  | d|     | d   |    d|
+  +--+--+--+  +--+--+  +  +--+  +--+  +--+  +--+--+  +--+--+  +--+  +--+  +--+  +  +--+--+  +--+--+--+  +
|  |     |   u |  |   u |  |   u |  |  | d|  |u | d|  |u | d|  |u |  |  | d   |  | d   |  | d   |     |  |
+--+  +--+--+--+  +--+--+  +--+--+  +--+--+--+  +  +  +  +  +--+--+--+  +--+--+  +--+--+  +--+--+--+  +--+
|   u |u    |  |u    |  |  |  | d| d|  |    d|  |  |  |  |  |u    |  |u |u |  |  |  |    d|  |    d| d   |
+--+--+  +--+  +--+--+  +  +  +--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+  +  +  +--+--+  +--+  +--+--+
|u |  |  |  |   u |   u |  | d   |   u |u | d|  | d|  |u |  |u | d| d   |   u |  | d   | d   |  |  |  | d|
+  +  +--+  +--+  +--+--+  +--+--+--+--+  +--+  +  +  +  +  +--+  +--+--+--+--+  +--+--+  +--+  +--+  +  +
|  |u    |u    |  |u    |  |    d|    d|  |    d|  |  |  |u    |  |u    |u    |  |    d|  |    d|    d|  |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 1                     level 2                    level 3                    level 4


5x8x8 co-minimal, by Helmut Postl
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|u |     |u |     |  |u |  | d   |u   d|   u |u   d|  |u |  | d|u |  | d| d|u |
+--+  +--+--+  +--+  +--+  +  +--+  +--+--+  +--+  +  +--+  +--+--+  +--+--+--+
|   u |  |   u |u |u    |  |u | d|  |u | d| d| d|  |  | d|   u | d   |u |     |
+--+--+  +--+--+--+--+  +  +--+--+--+--+--+--+--+--+  +--+--+  +  +--+--+  +--+
|  |u |   u |u |     |  |  |u   d|  | d| d   |   u |  | d|u |  |  |u |   u | d|
+  +--+--+  +--+  +--+--+  +  +--+  +--+  +--+--+  +  +--+--+--+--+--+--+--+--+
|   u |u |  |   u |  |u |  |  | d| d u |u | d|u | d|  |     |u | d| d|    d|u |
+--+  +--+--+--+--+  +--+  +--+--+--+--+--+--+--+--+  +--+  +--+--+--+--+  +--+
|u |  |u    |  |u |u    |  | d|u | d|u |u   d| d|  |  |u | d   | d| d|u |     |
+--+--+  +--+  +--+--+  +  +  +--+--+  +--+  +--+  +  +--+--+--+--+--+--+--+--+
|  |     |u |u    |u |  |  |u    |    d| d|  | d u |  | d|u    |u |  |  |u | d|
+  +--+--+--+--+  +--+--+  +--+--+--+--+--+--+--+--+  +--+  +--+--+  +  +--+--+
|   u |u |u    |  |u    |  |  | d| d| d|u |  | d|u |  |     |u |    d|u    | d|
+--+  +--+  +--+--+  +--+  +  +--+  +--+--+  +--+  +  +--+--+--+  +--+--+  +--+
|u |  |     |u |     |u |  | d u |u    | d u |    d|  |u | d| d|  |u | d|  |u |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 1                     level 2                    level 3

+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
| d|u |u   d|   u |u   d|  |    d| d|     | d| d|  |
+  +--+--+  +--+  +  +--+  +--+  +--+--+  +--+--+  +
|u    | d|  |u | d|  |u |  | d|     |  | d   |    d|
+--+--+--+--+--+--+--+--+  +--+--+--+  +--+--+  +--+
|u   d|  |u | d   | d|u |  | d|  |    d|     |  | d|
+  +--+  +--+  +--+--+  +  +--+  +  +--+--+  +--+--+
|  |u | d u |u |u |    d|  |    d|  | d| d| d   |  |
+--+--+--+--+--+--+--+--+  +  +--+--+--+--+--+--+  +
| d   |u |u |u   d|u |  |  |  |    d| d| d|  | d   |
+  +--+--+  +--+  +--+  +  +--+--+  +--+--+  +  +--+
|u | d|    d|u |  | d u |  | d|  |     | d   |  | d|
+--+--+--+--+--+--+--+--+  +--+  +--+--+  +--+--+--+
|u |  | d|u |  | d|   u |  | d   |    d|  |     | d|
+--+  +  +--+  +--+--+  +  +  +--+--+  +--+--+  +--+
| d u |u    | d u |u | d|  |  | d| d|     | d| d   |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 4                     level 5


also: 4x7x30, 4x7x35, 4x7x40, 4x7x45, 4x7x50, 4x7x55, 4x8x15, 4x10x12, 4x10x13,
      5x6x12, 5x6x13, 5x6x14, 5x6x15, 5x6x16, 5x6x17, 5x6x18, 5x6x19, 5x6x20,
       5x6x21, 5x6x22, 5x6x23, 5x7x16, 5x7x19, 5x7x21, 5x8x10, 5x8x11, 5x8x12,
       5x8x13, 5x8x14, 5x8x15, 5x8x17, 6x7x10, 6x8x10, 6x9x10
also: 4x10x10, 6x10x10 by George Sicherman


same pentacube, allowing reflections

4x5x7 minimal by Patrick Hamlyn
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
|   u |   u |  |  |u | d|u | d   |  | d|u   d|u    |  |  | d|    d|  |
+--+  +--+  +  +  +  +--+--+--+--+  +--+--+  +  +--+  +  +--+--+--+  +
|u |     |  |u |  | d   |  |    d|  |u    |  |  |u |  | d|  |  |    d|
+--+--+--+--+--+  +--+--+  +--+  +  +  +--+--+--+  +  +--+  +  +--+--+
|u |  |u |     |  | d   | d u |  |  |  |u |u | d|  |  |    d| d   |  |
+--+  +--+  +--+  +  +--+--+--+--+  +--+--+  +--+--+  +  +--+--+--+  +
|   u |   u |  |  |u | d|  | d|u |  | d|u |  |u | d|  |  | d   | d   |
+  +--+--+--+  +  +--+--+  +--+--+  +--+--+--+--+  +  +--+  +--+  +--+
|  |   u |u    |  |  |u | d| d|  |  |  | d u |   u |  |     | d|  | d|
+--+--+  +  +--+  +  +--+--+--+  +  +  +--+  +--+--+  +--+--+--+--+--+
|u    |  |  |u |  | d|  |  |    d|  |u    |  |   u |  | d|  |     | d|
+  +--+--+--+  +  +--+  +  +--+--+  +--+--+--+--+  +  +  +  +--+  +--+
|  |u    |u |  |  |    d|u   d|u |  |   u | d|u | d|  |  | d   | d   |
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
level 1            level 2           level 3           level 4

also: 2x9x15, 2x9x20, 2x9x25, 2x10x10, 2x10x12, 2x10x14, 2x10x15, 2x10x16,
       2x10x17, 2x10x18, 2x10x19, 2x10x21, 2x10x23, 2x12x15,
      4x5x9, 4x5x10, 4x5x11, 4x5x12, 4x5x13, 4x5x15, 4x6x10, 4x6x15,
      5x5x8, 5x5x10, 5x5x11, 5x5x13, 5x6x7, 5x6x8, 5x6x9, 5x6x10, 5x6x11,
       5x6x12, 5x6x13,
      6x6x10, 6x6x15

...............................................................................

*2
2


4x9x15 minimal
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|u    |   u |u |   u |u    |   u |u    |   u |
+--+  +  +--+  +  +--+--+  +  +--+--+  +  +--+
|  |  |  |  |  |  |     |  |  |     |  |  |  |
+  +--+--+  +--+--+  +--+--+--+--+  +--+--+  +
|u |     |   u |u |u |     |u    |u |u    |u |
+--+--+  +--+--+  +--+  +--+--+  +--+--+  +--+
|u    |u |  |  |   u |u |     |  |  |  |  |u |
+--+  +--+  +  +--+--+--+--+  +--+  +  +--+  +
|  |  |u |u |   u |u |u    |u |u    |u |  |  |
+  +--+  +--+--+--+  +--+  +--+--+--+--+  +--+
|u |  |   u |u |u    |u |u |u |u    |u |   u |
+--+  +--+--+  +--+--+  +--+  +--+  +  +--+--+
|u |   u |u    |u |     |u    |u |u |     |u |
+  +--+--+--+--+  +--+--+--+--+  +--+--+--+  +
|  |  |  |  |     |  |  |  |     |  |  |  |  |
+--+  +  +  +--+--+  +  +  +--+--+  +  +  +--+
|u    |u |   u |u    |u |   u |u    |u |   u |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 1

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| d|u    | d| d   | d| d|u    | d| d|   u | d|
+  +--+  +  +--+  +  +  +--+  +  +  +  +--+  +
|  |  |u |  |  |  |  |  |  |  |  |  |u |  |  |
+--+  +--+--+  +--+--+--+  +--+--+--+--+  +--+
| d   |u    | d| d| d   |u | d|    d| d|    d|
+--+--+--+  +--+--+--+--+--+  +--+--+  +--+--+
| d|    d|u |  |  | d| d   |  |  |  |  |    d|
+  +--+--+--+  +  +--+--+--+--+  +  +--+  +--+
|  |  | d| d   | d| d| d|    d| d|    d|  |  |
+--+  +--+--+--+--+--+--+--+--+--+--+--+--+  +
| d   |  | d| d| d|    d| d| d| d|u | d   | d|
+--+--+  +--+--+--+--+--+--+--+--+--+--+--+--+
| d   | d| d|    d|u    | d|    d| d|u |    d|
+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+
|  |  |u |  |  |  |  |  |  |  |  |  |u |  |  |
+  +--+--+  +  +  +  +--+  +  +  +  +--+--+  +
| d|u | d   | d| d|u | d   | d| d|    d|u | d|
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 2

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|u | d|u    |u |u |   u | d|u |u |   u | d|u |
+  +--+--+  +  +  +  +--+  +  +  +  +--+--+  +
|  |  | d|  |  |  |  |  |  |  |  |  | d|  |  |
+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+
|u    | d|u |u    |u |    d|u    |u |u |   u |
+--+--+--+--+--+--+--+--+--+--+--+--+  +--+--+
|u |   u | d|u |u |u |u    |u |u |u |  |   u |
+  +--+--+--+--+--+--+--+--+--+--+--+--+  +--+
|  |  |u    |u |u    |u |u |u |   u |u |  |  |
+--+  +--+  +  +--+--+--+--+  +  +--+--+--+  +
|u    |  |  |  |  |   u |u |  |  | d|u    |u |
+--+--+  +--+--+  +--+--+--+--+--+  +--+--+--+
|u    |u |u    |u | d|   u |u |u |    d|   u |
+--+  +--+--+--+--+  +--+--+--+  +--+--+  +--+
|  |  | d|  |  |  |  |  |  |  |  |  | d|  |  |
+  +--+  +  +  +  +--+  +  +  +--+  +  +--+  +
|u | d   |u |u |    d|u |u |   u |u |    d|u |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 3

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| d   | d|    d| d   | d|    d| d   | d|    d|
+--+  +  +  +--+--+  +  +  +--+--+  +  +  +--+
|  |  |  |  |     |  |  |  |     |  |  |  |  |
+  +--+--+--+  +--+--+--+--+  +--+--+--+--+  +
| d|     | d| d|    d|     | d|    d| d   | d|
+--+--+  +  +--+  +--+  +--+--+  +--+--+  +--+
| d   | d|    d| d| d| d|    d| d| d   |  | d|
+--+  +--+--+--+--+  +--+  +--+--+--+  +--+  +
|  |  | d|    d| d|    d| d| d   | d| d|  |  |
+  +--+  +  +--+  +--+--+--+--+  +  +--+  +--+
| d|  |  |  |  |     | d| d   |  |  | d|    d|
+--+  +--+--+  +--+--+  +--+  +--+--+  +--+--+
| d|    d| d|    d|     | d| d| d   |     | d|
+  +--+--+  +--+--+--+--+  +--+--+  +--+--+  +
|  |  |  |     |  |  |     |  |  |  |  |  |  |
+--+  +  +--+--+  +  +--+--+  +  +--+  +  +--+
| d   |    d| d   |    d| d   | d| d   |    d|
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 4

also: 4x9x20 by Helmut Postl
also: 4x9x25, 6x7x15
also: 8x8x10 by George Sicherman

...............................................................................

*2*
 *


7x8x20 by Helmut Postl
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|  |   u    |   u    |  |u |   u    |u |u |  |   u    |  |u |
+  +--+  +--+--+  +--+  +--+--+  +--+--+--+  +--+  +--+  +--+
|u    |  |u |  |  |u |u    |u |  |  |  |   u    |  |u |u    |
+  +--+--+--+  +--+--+  +--+--+--+  +  +--+--+--+--+--+  +--+
|  |   u    |u    |  |  |u |  |   u |u    |  |   u    |  |u |
+--+--+  +--+  +--+  +--+--+  +--+  +  +--+  +--+  +--+--+--+
|u |  |  |u |  |  |u    |   u |  |  |  |  |u    |  |   u    |
+--+  +--+--+--+  +  +--+--+  +  +--+--+  +  +--+--+--+  +--+
|   u    |  |   u |  |  |  |  |u    |   u |  |  |u |  |  |u |
+--+--+--+  +--+  +--+  +  +--+  +--+--+  +--+  +--+  +--+--+
|u |  |   u    |  |   u |u    |  |u |  |  |   u |   u    |  |
+--+  +--+--+--+--+--+  +  +--+--+--+  +--+--+  +--+--+--+  +
|   u |u |  |   u    |  |  |  |u |   u |u |  |  |u |  |   u |
+--+  +--+  +--+  +--+--+--+  +--+--+  +--+  +--+--+  +--+  +
|u |  |   u    |  |u |u |   u    |u |  |   u    |   u    |  |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 1

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|u |  | d|  |u | d|  |   ud|  | d|   ud|ud   |u | d|  |   ud|
+--+  +--+  +--+--+  +--+  +  +--+--+  +  +--+--+--+  +--+  +
| d|u    | d   |    d| d|  |ud   |u |  |  | d|  |    d| d|  |
+--+  +--+  +--+--+  +--+--+--+--+--+--+--+--+  +--+  +--+--+
|  |  | d|  | d|u |  |    d   |u | d| d|u |   u | d|  |   ud|
+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+  +
|ud   |    d   |u | d|  |  | d|u |   u    | d|  |  |u | d|  |
+--+--+--+  +--+--+--+  +--+--+--+--+  +--+--+--+  +--+--+--+
|  | d|u |  |  | d|   u    |u | d|  |  | d|u |    d   |   ud|
+  +--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +
|ud   |  | d|u    |u | d| d|u |    d   |  |u | d|  | d|  |  |
+--+--+  +--+  +--+--+--+--+--+--+--+--+  +--+--+  +--+  +--+
|  | d| d   |  | d|  |  |u |   ud|  | d| d   |    d|   u | d|
+  +--+  +--+--+--+  +  +--+--+  +  +--+  +--+--+  +--+  +--+
|ud   |  | d|u |   ud|ud   | d|  |ud   |  | d|u |  | d|  |u |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 2

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|ud   |u |    d   |u |  | d|u |u |  | d| d|  |ud   |u |  | d|
+  +--+--+--+  +--+--+  +--+--+--+  +--+--+  +  +--+--+  +--+
|  | d|  |u |  |  |   u |  | d|  |ud   |   u |  |u |   u    |
+--+--+  +--+--+  +--+  +  +--+  +--+--+--+  +--+--+--+--+--+
|u |   u |u |  |ud   |  |u    |ud   |   ud|  | d|u |  |  | d|
+--+--+  +--+  +--+--+--+  +--+--+--+--+  +--+--+--+  +  +--+
| d|  |  |   u |ud   |u |  |  |ud   | d|  |  |  |   ud|u    |
+--+  +--+--+  +  +--+--+--+  +  +--+--+--+  +  +--+--+  +--+
|   u |ud   |  |  |  | d|   ud|  |  |u |   ud|u    |  |  | d|
+--+  +  +--+--+--+  +--+--+--+--+  +--+--+--+  +--+  +--+--+
| d|  |  |u | d|  |ud   |   ud|   u |  |   ud|  |u |u    |u |
+--+--+--+--+--+  +--+--+--+  +--+  +  +--+  +--+--+  +--+--+
|   u    |u |  |u    |   ud|  | d|  |u    |  |  |u |  | d|  |
+--+  +--+--+  +  +--+--+  +--+--+--+  +--+--+  +--+--+--+  +
| d|  |u |   ud|  | d| d|  |u |u | d|  |u |    d   |u |   ud|
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 3

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| d|   ud|  |u |    d   |   ud|ud   |   u    | d|  |ud   |u |
+--+--+  +  +--+--+  +--+--+  +  +--+--+  +--+--+  +  +--+--+
|  |u |  |ud   |u |  | d|u |  |  | d|u |  | d|   ud|  | d|  |
+  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+  +
| d   | d|ud   | d|u |  | d|u | d|u |  | d|u |   ud|u |   u |
+  +--+--+  +--+--+--+  +--+--+--+--+  +--+--+--+  +--+--+  +
|  |u |u |  | d| d|    d   |u | d|   u    |u |u |  | d| d|  |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|  | d| d|  |u |u |   u    | d|u |    d   | d| d|  |u |u |  |
+  +--+--+  +--+--+--+  +--+--+--+--+  +--+--+--+  +--+--+  +
|u    |u |ud   |u | d|  |u | d|u | d|  |u | d|   ud| d|    d|
+  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+  +
|  | d|  |ud   | d|  |u | d|  |  |u | d|  |u |   ud|  |u |  |
+--+--+  +  +--+--+  +--+--+  +  +--+--+  +--+--+  +  +--+--+
|u |   ud|  | d|   u    |   ud|ud   |    d   |u |  |ud   | d|
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 4

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|u |  | d|   ud|  |u |u |  | d| d|u |  | d|   u    | d|   ud|
+--+  +--+--+  +  +--+--+  +--+--+--+  +--+--+  +--+--+--+  +
|    d   | d|  | d   |   ud|  |u |  | d   |  |  | d|  |u |  |
+--+--+--+--+--+  +--+--+--+  +--+  +  +--+  +--+--+  +--+--+
|u |  |  | d|u |  |ud   |   ud|    d|  |   ud|  | d| d   | d|
+--+  +  +--+--+--+  +--+--+--+--+  +--+--+--+  +--+  +--+--+
|    d|ud   |  |  |  |u |   ud|  |  | d|   ud| d   |  |  |u |
+--+  +--+--+  +  +--+--+--+  +  +--+--+--+  +  +--+--+  +--+
|u |  |  |    d|ud   | d|  |  |ud   |u |  |  |  |   ud| d   |
+--+--+  +--+  +--+--+--+  +--+--+--+--+  +--+--+--+  +  +--+
| d|    d| d|  |ud   |  | d   |ud   |   ud|  |u | d|  |  |u |
+--+--+  +--+--+  +--+  +  +--+  +--+--+--+  +--+--+--+--+--+
|  |u |  | d|  |  |    d|  |u |  |ud   |    d|  | d|    d   |
+  +--+--+--+  +--+--+  +--+--+--+  +--+--+  +  +--+--+  +--+
|ud   | d|   u    | d|  |u | d| d|  |u |u |  |ud   | d|  |u |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 5

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|ud   |  |u | d|   ud|ud   |u |  |ud   |  |u | d|  |u |  | d|
+  +--+  +--+--+--+  +  +--+--+  +  +--+  +--+--+  +--+  +--+
|  |u |u    |  |u |  |  | d|   ud|  |u |u    |   u |    d|u |
+--+--+  +--+  +--+--+--+--+--+--+--+--+  +--+--+  +--+  +--+
|ud   |  |u | d   | d|u |u | d|   u    |  | d|u |  |u |  |  |
+  +--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +
|  |u | d|  |  |u |    d   | d|u |  |  |u | d|   u    |   ud|
+--+--+--+  +--+--+--+  +--+--+--+--+  +--+--+--+  +--+--+--+
|ud   |   u    | d|u |  |  |u | d|    d   |u |  |  | d|u |  |
+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+  +
|  |  |u |  |u | d|  |   u    | d|u |u | d|    d|u |  |   ud|
+--+  +--+  +--+--+  +--+--+--+--+--+--+--+--+  +--+  +--+--+
|u | d   |u    |   u |u |  |ud   | d|  |  |u |  |   u |u |  |
+--+  +--+  +--+--+  +--+  +  +--+--+  +  +--+--+--+  +--+  +
| d|  |u |  | d|u |  |   ud|  |u |   ud|ud   | d|u |  |   ud|
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 6

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| d|  |    d   |  | d| d|    d   | d|  |    d   |    d   |  |
+--+  +--+  +--+  +--+--+--+  +--+--+  +--+  +--+--+  +--+  +
|    d| d|  |    d   |  |  |  | d|    d| d|  |  | d|  |    d|
+--+  +--+--+--+--+--+  +  +--+--+--+  +--+--+  +--+--+--+  +
| d|  |    d   |  |    d| d   |  | d|  |  |    d|    d   |  |
+--+--+--+  +--+  +--+  +  +--+  +--+--+  +--+  +--+  +--+--+
|    d   |  |    d|  |  |  |  | d   |    d|  |  | d|  |  | d|
+--+  +--+--+--+  +  +--+--+  +  +--+--+  +  +--+--+--+  +--+
| d|  |  | d|  |  | d   |    d|  |  |  |  | d   |  |    d   |
+--+--+  +--+  +--+  +--+--+  +--+  +  +--+  +--+  +--+--+--+
|  |    d   | d   |  |  | d|  |    d| d   |  |    d   |  | d|
+  +--+--+--+  +--+--+  +--+--+--+  +  +--+--+--+--+--+  +--+
| d   |  | d|  |  | d| d   | d|  |  |  |    d   |  | d| d   |
+  +--+  +--+--+  +--+  +--+--+  +--+--+--+  +--+  +--+  +--+
|  |    d   |    d   |  | d|    d   | d| d|  |    d   |  | d|
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 7

also: 6x8x25
also: 10x10x12 by George Sicherman

...............................................................................
Hexacubes
...............................................................................


*
*****


1x2x6 minimal
+--+--+--+--+--+--+
|  |              |
+  +--+--+--+--+  +
|              |  |
+--+--+--+--+--+--+

also: 1x7x12, 1x8x15, 1x9x14, 1x9x16, 1x9x34, 1x10x15, 1x11x18
      2x4x21, 2x7x9, 2x8x9, 2x9x9,
      3x4x22, 3x4x23, 3x4x26, 3x4x27, 3x4x31, 3x5x8, 3x5x10, 3x7x8, 3x7x10,
       3x8x8, 3x8x9, 3x9x10
also: 3x5x6 by Andrew Clarke
also: 2x5x9 by Keiichiro Ishino

...............................................................................

**
****


1x2x6 co-minimal
+--+--+--+--+--+--+
|     |           |
+     +--+--+     +
|           |     |
+--+--+--+--+--+--+


1x3x4 co-minimal
+--+--+--+--+
|           |
+--+--+     +
|     |     |
+     +--+--+
|           |
+--+--+--+--+

also: 1x5x18, 1x6x11, 1x9x10, 3x3x10, 3x5x6

...............................................................................

* *
****


1x3x4 minimal
+--+--+--+--+
|           |
+--+  +--+  +
|  |  |  |  |
+  +--+  +--+
|           |
+--+--+--+--+

also: 2x5x12

...............................................................................

*
**
***


1x3x4 minimal
+--+--+--+--+
|  |        |
+  +--+     +
|     |     |
+     +--+  +
|        |  |
+--+--+--+--+

also: 5x5x12

...............................................................................

  *
* *
***


1x3x4 minimal
+--+--+--+--+
|        |  |
+  +--+  +  +
|  |  |  |  |
+  +  +--+  +
|  |        |
+--+--+--+--+

also: 3x5x6, 3x6x7, 5x5x6
also: 3x6x6 by Torsten Sillke

...............................................................................

 **
****


1x4x6 minimal
+--+--+--+--+--+--+
|  |           |  |
+  +--+     +--+  +
|     |     |     |
+     +--+--+     +
|     |     |     |
+  +--+     +--+  +
|  |           |  |
+--+--+--+--+--+--+

also: 1x5x12,
      2x5x18, 2x7x12, 2x7x18, 2x9x20, 2x9x22, 2x9x26, 2x9x28, 2x10x15, 2x10x21,
       2x14x15, 2x14x21, 2x15x16,
      3x4x4, 3x5x30, 3x9x18, 3x10x10, 3x11x18,
      5x5x18, 5x6x9, 5x6x10, 5x6x11,
      6x6x9, 6x6x10, 6x6x11, 6x7x7, 6x7x9, 6x7x10

...............................................................................

*
***
**


3x4x5 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
|  |u |   u  u |  |  |ud u |ud  d|  |    d  d| d|  |
+  +--+--+--+--+  +  +--+--+--+--+  +--+--+--+--+  +
|        |     |  |        |     |  |     |        |
+     +--+     +  +     +--+     +  +     +--+     +
|     |        |  |     |        |  |        |     |
+--+--+--+--+  +  +--+--+--+--+  +  +  +--+--+--+--+
|u  u    |u |  |  | d ud|u  ud|  |  |  | d| d  d   |
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
level 1            level 2           level 3


also: 1x9x12 by David Klarner
also: 1x9x20, 1x9x28, 1x12x13, 1x12x14, 1x12x17, 1x12x19, 1x12x21,
      1x12x24, 1x12x25, 1x12x29, 1x15x28, 1x15x32, 1x15x36, 1x15x40,
      1x15x44, 1x15x48, 1x15x52, 1x16x18, 1x16x27, 1x16x30, 1x16x33,
      1x16x39, 1x16x42, 1x20x21, 1x20x24
also: 3x6x6 by Torsten Sillke
also: 3x3x8, 3x3x12, 3x4x6, 3x4x7, 3x4x9, 3x5x10, 3x6x7, 3x6x9, 4x4x6, 4x4x9,
      5x5x6, 5x6x6, 5x6x7

...............................................................................

 *
*****


2x7x12 minimal by Patrick Hamlyn
+--+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+--+
|  |  |  |  |  |  |u |         u    |  |              |    d         | d|  |
+  +  +  +  +  +  +--+--+--+--+--+--+  +--+--+--+  +--+--+--+--+--+--+--+  +
|u |u |u |  |u |  |u |         u    |  | d| d| d|  | d|    d         | d|  |
+  +  +  +  +  +  +--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+  +
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |              |              |  |
+  +  +  +  +  +  +  +  +  +  +  +  +  +  +--+  +--+--+--+--+  +--+--+--+  +
|  |  |  |u |  |u |u |  |u |  |  |  |  |     |  | d|  | d| d|  | d|  |     |
+  +  +  +  +  +  +  +  +  +  +  +  +  +  +--+--+--+  +--+--+--+--+  +--+  +
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |              |              |  |
+--+--+--+--+--+--+  +  +  +  +  +  +  +  +--+--+--+--+--+--+--+--+--+--+--+
|   u          |u |  |u |  |u |u |u |  |  | d|          d   | d|  | d| d| d|
+--+--+--+--+--+--+  +  +  +  +  +  +  +  +--+--+--+--+--+--+--+  +--+--+--+
|   u          |u |  |  |  |  |  |  |  |  | d|          d   |              |
+--+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+--+
level 1                                 level 2

also: 1x23x24 (by T.W. Marlow and Karl A. Dahlke, independently)
also: 3x5x12 by Andrew Clarke
also: 4x5x9 by Keiichiro Ishino
also: 2x5x24, 2x5x60, 2x5x66, 2x5x78, 2x7x18, 2x8x15, 2x8x18, 2x8x21, 2x8x24,
       2x8x27, 2x9x16, 2x9x18, 2x9x20, 2x9x22, 2x9x24, 2x9x26, 2x9x28, 2x9x30,
       2x10x12, 2x10x15, 2x10x18, 2x10x21, 2x11x12, 2x11x18, 2x12x12, 2x12x13,
       2x12x15, 2x12x16, 2x13x18, 2x14x15, 2x14x21,
      3x5x16, 3x5x20, 3x6x16, 3x6x20, 3x6x22, 3x6x24, 3x6x26, 3x6x28, 3x6x30,
       3x6x34, 3x7x16, 3x7x20, 3x7x24, 3x7x28, 3x8x10, 3x8x16, 3x8x17, 3x8x18,
       3x8x19, 3x8x21, 3x8x22, 3x8x23, 3x8x24, 3x8x25, 3x9x16, 3x9x20, 3x9x24,
       3x9x28, 3x11x12, 3x12x12, 3x12x13, 3x12x14,
      4x5x12, 4x5x15, 4x6x10, 4x6x15, 4x6x16, 4x6x18, 4x6x19, 4x6x21, 4x6x22,
       4x6x23, 4x6x24, 4x6x27, 4x7x15, 4x7x21, 4x8x12, 4x9x11, 4x9x12,
       4x9x13, 4x9x14,
      5x5x12, 5x6x6, 5x6x8, 5x6x10,
      6x6x11, 6x6x12, 6x6x13, 6x6x14, 6x7x8, 6x7x10, 6x7x14, 6x8x8,
       6x8x9, 6x8x11

...............................................................................

*
***
* *


3x4x5 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
|   u    |     |  |u |ud|        |  | d| d   |     |
+--+--+--+  +--+  +  +--+--+  +--+  +--+--+--+  +--+
|        |  |u |  |  |     |  |ud|  |        |  | d|
+--+  +--+  +--+  +  +  +--+  +  +  +--+  +--+  +--+
|u |  |        |  |ud|  |     |  |  | d|  |        |
+--+  +--+--+--+  +--+  +--+--+  +  +--+  +--+--+--+
|     |   u    |  |        |ud|u |  |     |    d| d|
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
level 1            level 2           level 3


also: 3x8x8, 3x10x106, 3x11x48, 4x4x6, 4x4x9, 4x6x9, 4x6x11, 4x7x9, 4x7x12, 5x6x26

...............................................................................

*  *
****


   +--+--+        +--+--+
   |u |u |        | d| d|
+--+--+--+--+  +--+  +  +--+
|u        u |  | d|  |  | d|
+--+--+--+--+  +--+  +  +--+
|u        u |  | d|  |  | d|
+--+--+--+--+  +--+  +  +--+
   |u |u |        | d| d|
   +--+--+        +--+--+
level 1         level 2


2x4x6 (confirmed co-minimal by Patrick Hamlyn)
+--+--+--+--+--+--+
|     |     |     |
+  +--+     +--+  +
|  |           |  |
+  +           +  +
|  |           |  |
+  +--+     +--+  +
|     |     |     |
+--+--+--+--+--+--+
(2 levels deep)


   +--+--+        +--+--+        +--+--+        +--+--+
   |u |u |        |ud|ud|        |ud|ud|        | d| d|
+--+  +  +--+  +--+--+--+--+  +--+--+--+--+  +--+  +  +--+
|u |  |  |u |  | d        d|  |u        u |  | d|  |  | d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4


3x4x4 (confirmed co-minimal by Patrick Hamlyn)
+--+--+--+--+
|           |
+  +--+--+  +
|  |     |  |
+--+     +--+
|           |
+--+--+--+--+
(4 levels deep)

also: 4x5x6 by David Klarner and Frits Go"bel
also: 6x10x13, 6x10x14, 6x10x19, 6x11x18, 6x14x15

...............................................................................

* **
***


3x4x6 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|     |u     u |  |  |   u | d|u | d   |  |  | d     d|     |
+--+  +--+--+--+  +  +--+--+--+--+--+--+  +  +--+--+--+  +--+
|u |  |u    |     |  | d     d|u     u |  |     |    d|  | d|
+--+  +--+--+  +--+  +--+--+--+--+--+--+  +--+  +--+--+  +--+
|     |   u |  |u |  |u     u | d     d|  | d|  | d   |     |
+  +--+--+--+  +--+  +--+--+--+--+--+--+  +--+  +--+--+--+  +
|  |u     u |     |  |    d|u | d|u    |  |     | d     d|  |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3


also: 4x5x12, 5x6x12, 6x6x7, 6x6x9
also: 6x6x6 by Torsten Sillke

...............................................................................

 **
**
**


3x4x5 minimal by Helmut Postl
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
|u  u |u |     |  | d ud| d u  u |  |  | d   | d  d|
+--+--+--+     +  +--+--+--+--+--+  +  +--+--+--+--+
|u |u  u |     |  |ud| d  d u |u |  | d|     | d| d|
+  +--+--+  +--+  +  +--+--+--+  +  +--+  +--+--+  +
|u |u |     |u |  | d| d u  u |ud|  |     | d  d| d|
+--+--+--+--+  +  +--+--+--+--+--+  +     +--+--+--+
|u  u |   u |  |  | d  d u |ud u |  |     | d| d  d|
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
level 1            level 2           level 3


also 3x4x6
+--+--+--+--+--+--+  +--+--+--+--+--+--+
|  |u    |   u |  |  |    d|     | d   |
+  +--+--+--+--+  +  +--+--+     +--+--+
|u |     |        |  | d|  |        |  |
+--+     +     +--+  +  +  +--+--+  +  +
|        |     |u |  |  |        |  | d|
+  +--+--+--+--+  +  +--+--+     +--+--+
|  |u    |   u |  |  |    d|     | d   |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               levels 2, 3

also: 3x6x6 by Torsten Sillke
also: 3x4x6, 3x4x7, 3x4x8, 3x4x9, 3x5x6, 3x6x7, 5x5x6

...............................................................................

*
*
****


+--+              +--+
|u |              | d|
+--+              +  +
|  |              |  |
+  +              +  +
|  |              |  |
+  +--+--+--+--+  +  +--+--+--+--+
|           |u |  |  |          d|
+--+--+--+--+--+  +--+--+--+--+--+
levels 1, 2        level 3


3x4x7 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+--+
|  |  |              |
+  +  +--+--+--+--+  +
|  |  |           |  |
+  +  +--+--+--+  +  +
|  |           |  |  |
+  +--+--+--+--+  +  +
|              |  |  |
+--+--+--+--+--+--+--+
(3 levels deep)


also: 3x5x10, 3x5x22, 3x5x24, 3x5x26, 3x5x28,
       3x6x8, 3x6x9, 3x6x10, 3x6x11, 3x6x12, 3x6x13, 3x6x14, 3x6x15,
       3x7x10, 3x8x8, 3x8x9, 3x8x10, 3x8x11, 3x9x10,
      4x4x9, 4x5x6, 4x5x9, 4x6x6,
      5x5x6, 5x6x6, 5x6x7,
      6x6x7, 6x7x7
also: 4x4x6 by Helmut Postl
also: 6x6x6 by Torsten Sillke

...............................................................................

 *
***
* *


3x5x6 minimal by Andrew Clarke
+--+--+--+--+--+--+  +--+--+--+--+--+--+
|   x |     |x    |  |  |x    |   x |  |
+--+--+  +--+--+--+  +  +--+--+--+--+  +
|x |     |x    |x |  |x |  |   x |  |x |
+  +--+  +--+--+  +  +--+  +--+--+  +--+
|  |x |     |x |  |  |  |x |     |x |  |
+--+  +--+--+  +--+  +  +--+  +--+--+  +
|x |  |   x |  |x |  |x |     |x    |x |
+  +--+--+--+--+  +  +--+--+  +--+--+--+
|  |x    |   x |  |  |   x |     |x    |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
levels 1, 3           level 2

also: 3x6x6 by Torsten Sillke
also: 3x6x7, 3x6x8, 3x6x9, 4x6x6, 5x6x7, 5x6x11, 6x8x8

...............................................................................

**
 *
 ***


+--+--+        +--+--+        +--+--+        +--+--+
|  |  |        |  |  |        |     |        |     |
+  +  +        +  +  +        +--+  +        +--+  +
|  |  |        |u |  |        |ud|  |        | d|  |
+  +  +--+--+  +--+  +--+--+  +--+  +--+--+  +  +  +--+--+
|u |        |  |ud|        |  | d|        |  |  |        |
+--+--+--+  +  +--+--+--+  +  +  +--+--+--+  +  +--+--+--+
|      u |  |  |   u |ud|  |  |  |ud| d   |  |  | d      |
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4


4x4x6 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+
|     |           |
+     +           +
|     |           |
+     +--+--+     +
|           |     |
+           +     +
|           |     |
+--+--+--+--+--+--+
(4 levels deep)

also: 4x4x21, 4x5x36, 4x5x39, 4x5x45, 4x6x6, 4x6x9, 4x6x11, 4x7x12, 4x9x20, ...

...............................................................................

*
***
  **


4x6x6 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|  |u |   u |     |  |  | d u |ud|     |  |     |ud| d u |  |  |     | d   | d|  |
+  +--+--+--+  +--+  +  +--+--+--+  +--+  +--+  +--+--+--+  +  +--+  +--+--+--+  +
|     |        |u |  |     |        | d|  |u |        |     |  | d|        |     |
+--+  +  +--+--+--+  +--+  +  +--+--+  +  +  +--+--+  +  +--+  +--+--+--+  +  +--+
|u |  |  |     |  |  |ud|  |  |     |u |  | d|     |  |  |ud|  |  |     |  |  | d|
+  +  +--+--+  +  +  +--+  +--+--+  +--+  +--+  +--+--+  +--+  +  +  +--+--+  +  +
|  |     |  |  |u |  |u |     |  |  |ud|  |ud|  |  |     | d|  | d|  |  |     |  |
+--+--+--+  +  +--+  +  +--+--+  +  +--+  +--+  +  +--+--+  +  +--+  +  +--+--+--+
|u |        |     |  | d|        |     |  |     |        |u |  |     |        | d|
+--+  +--+--+--+  +  +--+  +--+--+--+  +  +  +--+--+--+  +--+  +  +--+--+--+  +--+
|     |u    |u |  |  |     |ud|u   d|  |  |  |u   d|ud|     |  |  | d|    d|     |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4

also: 4x6x9, 4x6x10, 4x6x13, 4x6x14, 4x6x17

...............................................................................

**
 **
  **


3x6x8 minimal by Patrick Hamlyn
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|     |u    |u    |  |  |u   d|u   d|  |  |    d|    d|     |
+--+  +--+--+--+--+  +  +--+--+--+--+  +  +--+--+--+--+  +--+
|  |     |u    |  |  |     |u   d|     |  |  |    d|     |  |
+  +--+  +--+--+  +  +--+  +--+--+  +--+  +  +--+--+  +--+  +
|     |     |  |u |  |u |     |     | d|  | d|  |     |     |
+--+  +--+--+  +--+  +  +--+  +  +--+  +  +--+  +--+--+  +--+
|u |     |  |u |  |  | d|u |  |  | d|u |  |  | d|  |     | d|
+  +--+  +  +--+  +  +--+  +--+--+  +--+  +  +--+  +  +--+  +
|  |u |  |     |u |  |u | d|  |  |u | d|  | d|     |  | d|  |
+--+  +--+--+  +--+  +  +--+  +  +--+  +  +--+  +--+--+  +--+
|u |  |     |     |  | d|     |     |u |  |     |     |  | d|
+  +--+--+  +--+  +  +--+  +--+--+  +--+  +  +--+  +--+--+  +
|  |   u |     |  |  |     | d u |     |  |  |     | d   |  |
+--+--+--+--+  +--+  +  +--+--+--+--+  +  +--+  +--+--+--+--+
|   u |   u |     |  |  | d u | d u |  |  |     | d   | d   |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3

also: 3x6x10, 3x6x12, 3x6x13, 3x6x14, 3x6x15, 3x6x17, 3x6x19,
       3x7x12, 3x7x18, 3x9x12, 3x9x18, 3x11x12, 3x11x18,
      6x6x9, 6x6x11, 6x7x9, 6x7x15, 6x9x9, 6x9x11
also: 6x6x6 by Torsten Sillke

...............................................................................

 ****
**


2x6x8 minimal by Patrick Hamlyn
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|  |u          |  |u    |  |    d|  |          d|  |
+  +--+--+--+--+  +--+--+  +--+--+  +--+--+--+--+  +
|  |         u |  |  |u |  |  |     |  | d   |  | d|
+  +--+--+--+--+  +  +  +  +  +  +--+  +--+--+  +--+
|  |         u |  |  |  |  |  |  |     | d   |     |
+  +--+--+--+--+  +  +  +  +  +  +  +--+--+--+--+  +
|     |   u |     |  |  |  |  |  |  | d         |  |
+--+  +--+--+  +--+  +  +  +  +  +  +--+--+--+--+  +
|u |  |   u |  |     |  |  | d|  |  | d         |  |
+  +--+--+--+--+  +--+--+  +--+--+  +--+--+--+--+  +
|  |u          |  |u    |  |    d|  |          d|  |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 1                     level 2

also: 2x7x42, 2x7x72, 2x8x9, 2x9x14, 3x6x24, 3x6x30, ...

...............................................................................

  *
*****


5x5x6 minimal by Patrick Hamlyn
+--+--+--+--+--+--+  +--+--+--+--+--+--+
|  |x |  |x |  |x |  |   x |   x |   x |
+  +--+  +--+  +--+  +--+--+--+--+--+--+
|  |x |  |x |  |x |  |   x |  |x    |x |
+  +--+  +--+  +--+  +--+--+  +--+--+  +
|     |     |     |  |              |  |
+  +--+  +--+  +--+  +--+--+--+--+--+--+
|  |x |  |x |  |x |  |   x |   x |   x |
+  +--+  +--+  +--+  +--+--+--+--+--+--+
|  |x |  |x |  |x |  |   x |   x |   x |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
levels 1, 2, 4, 5     level 3

also: 5x6x6, 5x6x7, 5x6x8, 5x6x9

...............................................................................

***
 ***


4x6x7 minimal by Patrick Hamlyn
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|        |u  u    |  |u |  |    d  d|u |  |ud|  |u  u    |ud|  | d|    d  d|  | d|
+--+     +--+--+--+  +  +  +--+--+--+  +  +  +  +--+--+--+  +  +--+--+--+--+  +--+
|u |        |  |u |  |ud|     |u |  |ud|  | d|     |ud|  | d|  |        | d|     |
+--+--+--+--+  +--+  +--+     +  +  +--+  +--+     +  +  +--+  +--+     +--+     +
|        |u |     |  |  |     |ud|     |  |  |     | d|     |  |  |        |     |
+--+     +--+     +  +  +--+  +--+     +  +  +--+  +--+     +  +  +--+--+--+--+  +
|  |        |     |  |     |  |  |     |  |     |  |  |     |  |     |        |  |
+  +--+--+--+--+  +  +     +--+  +--+  +  +     +--+  +--+  +  +     +--+     +--+
|     |        |  |  |     |u |     |  |  |     |ud|     |  |  |     | d|        |
+     +--+     +--+  +--+  +  +     +--+  +--+  +  +     +--+  +--+  +--+--+--+--+
|     |u |        |  |u |  |ud|     |u |  |ud|  | d|     |ud|  | d|  |        | d|
+--+  +--+--+--+--+  +  +--+--+--+  +  +  +  +--+--+--+  +  +  +--+--+--+     +--+
|u |  |u  u    |u |  |ud|    d  d|  |ud|  | d|u  u    |  | d|  |    d  d|        |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4

also: 4x6x13, 4x6x16, 4x6x19, 4x6x22, 4x6x25, 4x6x31, 4x8x12, 4x8x18,
      4x9x30, 4x9x33, 4x9x36, 4x9x39, 4x9x42, 4x9x45, 4x10x12, 4x10x18,
      4x11x24, 4x12x15, 6x6x10, 6x6x13, 6x6x16, 6x6x19, 6x6x22, 6x6x25

...............................................................................

*
****
*


3x8x8 minimal by Patrick Hamlyn
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|  |x |x |x |x |        |  |  |x |x |x |x          |
+  +--+--+--+--+--+  +--+  +  +  +  +  +--+--+--+--+
|           |  |  |  |x |  |  |  |  |  |         x |
+  +--+--+--+  +  +  +--+  +  +  +  +  +--+--+--+--+
|  |           |  |  |x |  |  |  |  |  |         x |
+--+--+--+--+  +  +  +--+  +  +  +  +  +--+--+--+--+
|x |        |  |  |  |x |  |x |  |  |  |         x |
+--+--+  +--+--+  +--+--+  +--+--+--+--+--+--+--+--+
|x |  |  |  |        |x |  |x          |  |  |  |x |
+--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +  +
|x |  |  |           |  |  |x          |  |  |  |  |
+--+  +  +  +--+--+--+  +  +--+--+--+--+  +  +  +  +
|x |  |  |  |           |  |x          |  |  |  |  |
+--+  +--+--+--+--+--+  +  +--+--+--+--+  +  +  +  +
|        |x |x |x |x |  |  |         x |x |x |x |  |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
levels 1, 3                 level 2

also: 3x8x14, 3x8x17, 3x8x20, 3x8x21, ...

...............................................................................

****
 *
 *


6x6x8 minimal by Keiichiro Ishino
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|  |           |u |  |u |  |  |      ud|  |ud      |  |  | d|  | d|           |  |
+  +--+--+  +--+--+  +--+  +  +--+--+--+  +--+--+--+  +  +--+  +--+--+  +--+--+  +
|        |  |  |u |  |u |  |  |      ud|  |ud      |  |  | d|  | d|  |  |        |
+  +--+--+  +  +--+  +--+  +  +--+--+--+  +--+--+--+  +  +--+  +--+  +  +--+--+  +
|  |u |u |  |  |u |  |u |ud|ud|u |u |ud|  |ud| d| d|ud|ud| d|  | d|  |  | d| d|  |
+  +--+--+--+  +--+  +--+--+--+--+--+  +  +  +--+--+--+--+--+  +--+  +--+--+--+  +
|  |u |           |  |  |ud      |u |  |  |  | d|      ud|  |  |           | d|  |
+--+--+--+--+--+--+  +  +--+--+--+--+  +  +  +--+--+--+--+  +  +--+--+--+--+--+--+
|           |u |  |  |  |u |      ud|  |  |  |ud      | d|  |  |  | d|           |
+--+  +--+--+--+  +  +  +--+--+--+--+--+  +--+--+--+--+--+  +  +  +--+--+--+  +--+
|u |  |  |u |u |  |  |ud|u |u |ud|ud|u |  | d|ud|ud| d| d|ud|  |  | d| d|  |  | d|
+--+  +  +--+--+  +  +--+--+--+  +  +--+  +--+  +  +--+--+--+  +  +--+--+  +  +--+
|u |  |  |        |  |ud      |  |  |u |  | d|  |  |      ud|  |        |  |  | d|
+--+--+  +--+--+  +  +--+--+--+  +  +--+  +--+  +  +--+--+--+  +  +--+--+  +--+--+
|u |           |  |  |ud      |  |  |u |  | d|  |  |      ud|  |  |           | d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
levels 1, 2           level 3              level 4              levels 5, 6


+--+--+--+           +--+--+--+
|x |x |x |           |x |x |x |
+--+--+--+--+--+--+  +  +  +  +--+--+--+
|  |           |x |  |  |  |  |      x |
+  +--+--+  +--+--+  +  +  +  +--+--+--+
|        |  |  |x |  |  |  |  |      x |
+  +--+--+  +  +--+  +--+--+--+--+--+--+
|  |  |x |  |  |x |  |      x |      x |
+  +  +--+--+  +--+  +--+--+--+--+--+--+
|  |  |        |     |  |  |  |  |  |
+--+  +--+--+  +     +  +  +  +  +  +
|           |  |     |  |  |  |  |  |
+--+--+--+--+--+     +  +  +  +  +  +
|x |x |x |x |x |     |x |x |x |x |x |
+--+--+--+--+--+     +--+--+--+--+--+
levels 1, 2, 4        level 3


4x12x12
+--+--+--+--+--+--+--+--+--+--+--+--+
|                    |              |
+                    +              +
|                    |              |
+                    +              +
|                    |              |
+                 +--+              +
|                 |                 |
+                 +                 +
|                 |                 |
+--+--+--+        +                 +
|        |        |                 |
+        +--+--+--+--+--+--+        +
|                 |        |        |
+                 +        +--+--+--+
|                 |                 |
+                 +                 +
|                 |                 |
+              +--+                 +
|              |                    |
+              +                    +
|              |                    |
+              +                    +
|              |                    |
+--+--+--+--+--+--+--+--+--+--+--+--+
(4 levels deep)

also: 4x7x30, 4x8x12, 6x6x10, 6x6x12
also: 4x8x18 by Helmut Postl

...............................................................................

*
**
 ***


6x6x8 minimal by Keiichiro Ishino
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|        |u    |  |  |     |u   d|     |  |     |ud|u |     |
+--+--+  +--+--+  +  +--+  +--+--+  +--+  +--+  +--+--+  +--+
|     |     |  |u |  |u |     |     | d|  |ud|     |     |u |
+--+  +--+  +  +--+  +  +--+  +  +--+  +  +--+--+  +  +--+--+
|u |     |  |u |  |  | d|u |  |  | d|u |  |u |ud|  |  |u |ud|
+  +--+  +--+--+  +  +--+  +  +  +  +--+  +--+--+  +  +--+--+
|  |u |  |  |  |u |  |u | d|  |  |u | d|  |ud|u |  |  |ud|u |
+--+  +  +  +  +--+  +  +--+--+--+--+  +  +--+--+--+--+--+--+
|u |  |  |  |u |  |  | d|u |  |  | d|u |  |u |ud|  |  |u |ud|
+  +--+--+  +--+  +  +--+  +  +  +  +--+  +--+--+  +  +--+--+
|  |u |  |     |u |  |u | d|  |  |u | d|  |ud|u |  |  |ud|u |
+--+  +  +--+  +--+  +  +--+  +  +--+  +  +--+--+  +  +--+--+
|u |  |     |     |  | d|     |     |u |  |u |     |     |ud|
+  +--+--+  +--+--+  +--+  +--+--+  +--+  +--+  +--+--+  +--+
|  |   u |        |  |     | d u |     |  |     |u |ud|     |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3

+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|     | d|ud|     |  |     |u   d|     |  |  |    d|        |
+--+  +--+--+  +--+  +--+  +--+--+  +--+  +  +--+--+  +--+--+
| d|     |     |ud|  |u |     |     | d|  | d|  |     |     |
+--+--+  +  +--+--+  +  +--+  +  +--+  +  +--+  +  +--+  +--+
|ud| d|  |  |ud| d|  | d|u |  |  | d|u |  |  | d|  |     | d|
+--+--+  +  +--+--+  +--+  +  +  +  +--+  +  +--+--+  +--+  +
| d|ud|  |  | d|ud|  |u | d|  |  |u | d|  | d|  |  |  | d|  |
+--+--+--+--+--+--+  +  +--+--+--+--+  +  +--+  +  +  +  +--+
|ud| d|  |  |ud| d|  | d|u |  |  | d|u |  |  | d|  |  |  | d|
+--+--+  +  +--+--+  +--+  +  +  +  +--+  +  +--+  +--+--+  +
| d|ud|  |  | d|ud|  |u | d|  |  |u | d|  | d|     |  | d|  |
+--+--+  +  +--+--+  +  +--+  +  +--+  +  +--+  +--+  +  +--+
|ud|     |     | d|  | d|     |     |u |  |     |     |  | d|
+--+  +--+--+  +--+  +--+  +--+--+  +--+  +--+--+  +--+--+  +
|     |ud| d|     |  |     | d u |     |  |        | d   |  |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 4               level 5              level 6


also: 4x8x30 by Helmut Postl
also: 5x6x56, 5x6x66, 6x6x9, 6x6x10, 6x6x11, 6x6x12, 6x6x13, 6x6x14, 6x6x15

...............................................................................

 *
**
 ***


4x12x14 by Keiichiro Ishino
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|        |u       |u       |u       |  |  |
+--+--+  +--+--+--+--+--+--+--+--+--+  +  +
|u |u |     |u       |  |u       |  |  |  |
+  +  +  +--+--+--+--+  +--+--+--+  +  +  +
|  |  |  |        |        |  |     |u |u |
+  +  +--+  +--+--+--+--+  +  +--+  +--+--+
|  |  |     |u |      u |  |  |  |        |
+--+--+--+  +  +--+--+--+  +  +  +--+--+--+
|        |  |  |      u |  |u |     |  |  |
+--+--+  +--+  +--+--+--+--+--+  +--+  +  +
|u |u |     |  |      u |        |  |  |  |
+  +  +  +--+--+--+--+--+--+--+--+  +  +  +
|  |  |  |        |u       |  |     |u |u |
+  +  +--+  +--+--+--+--+--+  +--+  +--+--+
|  |  |     |u |  |u       |  |  |        |
+--+--+--+  +  +  +--+--+--+  +  +--+--+--+
|        |  |  |  |u       |u |     |  |  |
+--+--+  +--+  +  +--+--+--+--+  +--+  +  +
|u |u |     |  |        |        |  |  |  |
+  +  +  +--+--+--+  +--+--+--+--+  +  +  +
|  |  |  |      u |  |      u |     |u |u |
+  +  +--+--+--+--+--+--+--+--+--+  +--+--+
|  |  |      u |      u |      u |        |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 1

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|  |  |   ud|u |   ud|u |   ud|u |        |
+  +  +--+--+--+--+--+--+--+--+--+  +--+--+
|ud|ud|  |   ud|u |  |   ud|u |     |u |u |
+--+--+  +--+--+--+  +--+--+--+--+  +--+--+
|u |u |     |  |        |        |  |ud|ud|
+--+--+  +--+  +  +--+--+--+--+  +--+  +  +
|        |  |ud|  |u |ud   |u |     |  |  |
+--+--+--+  +--+  +--+--+--+--+  +--+--+--+
|  |  |     |u |  |u |ud   |ud|  |        |
+  +  +--+  +--+--+--+--+--+  +--+  +--+--+
|ud|ud|  |        |u |ud   |  |     |u |u |
+--+--+  +--+--+--+--+--+--+--+--+  +--+--+
|u |u |     |  |   ud|u |        |  |ud|ud|
+--+--+  +--+  +--+--+--+--+--+  +--+  +  +
|        |  |ud|   ud|u |  |u |     |  |  |
+--+--+--+  +--+--+--+--+  +--+  +--+--+--+
|  |  |     |u |   ud|u |  |ud|  |        |
+  +  +--+  +--+--+--+--+  +  +--+  +--+--+
|ud|ud|  |        |        |  |     |u |u |
+--+--+  +--+--+--+--+  +--+--+--+  +--+--+
|u |u |     |u |ud   |  |u |ud   |  |ud|ud|
+--+--+  +--+--+--+--+--+--+--+--+--+  +  +
|        |u |ud   |u |ud   |u |ud   |  |  |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 2

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|        | d|ud   | d|ud   | d|ud   |  |  |
+--+--+  +--+--+--+--+--+--+--+--+--+  +  +
| d| d|     | d|ud   |  | d|ud   |  |ud|ud|
+--+--+  +--+--+--+--+  +--+--+--+  +--+--+
|ud|ud|  |        |        |  |     | d| d|
+  +  +--+  +--+--+--+--+  +  +--+  +--+--+
|  |  |     | d|   ud| d|  |ud|  |        |
+--+--+--+  +--+--+--+--+  +--+  +--+--+--+
|        |  |ud|   ud| d|  | d|     |  |  |
+--+--+  +--+  +--+--+--+--+--+  +--+  +  +
| d| d|     |  |   ud| d|        |  |ud|ud|
+--+--+  +--+--+--+--+--+--+--+--+  +--+--+
|ud|ud|  |        | d|ud   |  |     | d| d|
+  +  +--+  +--+--+--+--+--+  +--+  +--+--+
|  |  |     | d|  | d|ud   |ud|  |        |
+--+--+--+  +--+  +--+--+--+--+  +--+--+--+
|        |  |ud|  | d|ud   | d|     |  |  |
+--+--+  +--+  +  +--+--+--+--+  +--+  +  +
| d| d|     |  |        |        |  |ud|ud|
+--+--+  +--+--+--+  +--+--+--+--+  +--+--+
|ud|ud|  |   ud| d|  |   ud| d|     | d| d|
+  +  +--+--+--+--+--+--+--+--+--+  +--+--+
|  |  |   ud| d|   ud| d|   ud| d|        |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 3

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|  |  |       d|       d|       d|        |
+  +  +--+--+--+--+--+--+--+--+--+  +--+--+
|  |  |  |       d|  |       d|     | d| d|
+  +  +  +--+--+--+  +--+--+--+--+  +  +  +
| d| d|     |  |        |        |  |  |  |
+--+--+  +--+  +  +--+--+--+--+  +--+  +  +
|        |  |  |  | d      | d|     |  |  |
+--+--+--+  +  +  +--+--+--+  +  +--+--+--+
|  |  |     | d|  | d      |  |  |        |
+  +  +--+  +--+--+--+--+--+  +--+  +--+--+
|  |  |  |        | d      |  |     | d| d|
+  +  +  +--+--+--+--+--+--+--+--+  +  +  +
| d| d|     |  |       d|        |  |  |  |
+--+--+  +--+  +--+--+--+--+--+  +--+  +  +
|        |  |  |       d|  | d|     |  |  |
+--+--+--+  +  +--+--+--+  +  +  +--+--+--+
|  |  |     | d|       d|  |  |  |        |
+  +  +--+  +--+--+--+--+  +  +--+  +--+--+
|  |  |  |        |        |  |     | d| d|
+  +  +  +--+--+--+--+  +--+--+--+  +  +  +
| d| d|     | d      |  | d      |  |  |  |
+--+--+  +--+--+--+--+--+--+--+--+--+  +  +
|        | d      | d      | d      |  |  |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 4


also: 4x8x36 by Helmut Postl

...............................................................................

  *
***
  **


6x8x30
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|   u |     |     |u |     |u |     |   u |  |  |  |  |  |u    |  |u    |  |  |   u |     |
+--+--+  +--+--+  +--+--+  +--+--+  +--+--+  +  +  +  +  +--+--+  +--+--+  +  +--+--+  +--+
|        |u    |        |        |        |  |u |u |  |        |  |        |  |        |u |
+--+--+  +--+--+  +--+--+  +--+--+  +--+--+  +--+--+  +--+  +--+  +--+  +--+  +--+--+  +--+
|u |  |  |u |  |  |u |  |  |u    |  |  |        |        |  |        |  |        |  |  |u |
+  +  +--+--+  +--+--+  +--+--+--+--+  +  +--+--+--+--+  +  +  +--+--+  +--+--+  +  +--+--+
|  |  |        |        |   u |        |  |u |  |     |  |  |  |     |  |     |  |        |
+--+  +--+--+  +--+--+  +--+--+--+--+  +--+  +  +--+  +--+--+--+--+  +--+--+  +--+--+  +--+
|        |  |     |  |     |  |  |  |     |  |u |  |        |u    |        |        |  |  |
+--+--+  +  +--+--+  +--+--+  +  +  +--+--+--+--+  +  +--+--+--+--+  +--+--+  +--+--+  +  +
|u |  |  |        |  |        |  |        |        |  |  |   u |  |  |u |  |  |u |  |  |u |
+--+  +--+--+  +--+  +--+  +--+  +--+  +--+--+  +--+--+  +--+--+  +--+--+  +--+--+  +--+--+
|u |        |  |        |  |        |  |u |u |  |        |        |        |   u |        |
+--+  +--+--+  +  +--+--+  +--+--+  +  +  +  +  +--+--+  +--+--+  +--+--+  +--+--+  +--+--+
|     |u    |  |  |   u |  |   u |  |  |  |  |  |u    |     |u |     |u |     |     |u    |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 1

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|  |ud      |u |  |ud      |ud|  |  |u |ud      |u |      ud|      ud|  |u |     |ud      |
+  +--+--+--+--+  +--+--+--+--+  +  +--+--+--+--+--+--+--+--+--+--+--+  +--+--+  +--+--+--+
|  |      ud|u |        |        |        |  |ud|ud|     |u    |        |u |  |        |ud|
+  +--+--+--+--+  +--+--+--+--+  +--+  +--+  +  +  +--+  +--+--+--+  +--+--+  +  +--+--+--+
|ud|      ud|     |ud|      ud|     |  |u |  |  |  |u |        |  |  |        |  |  |u | d|
+--+--+--+--+--+--+  +--+--+--+--+--+  +--+  +  +  +--+  +--+--+  +  +--+  +--+--+  +  +  +
|  |     |u    |  |  |     |ud      |  |u |ud|  |  |u |  |        |  |  |  |        |  |u |
+  +--+  +--+--+  +  +--+  +--+--+--+--+--+--+--+--+--+--+--+--+  +--+  +  +--+--+  +--+  +
|u |  |        |  |  |  |        |  |u |  |  |ud|u |  |      ud|     |  |  |   u |     |  |
+  +  +  +--+--+  +--+  +  +--+--+  +--+  +  +  +--+  +--+--+--+--+--+  +--+--+--+--+--+--+
| d|u |  |  |        |  |  |        |u |  |  |  |u |  |     |ud      |ud|     |ud      |ud|
+--+--+--+  +  +--+--+  +--+--+--+  +--+  +  +  +--+  +--+  +--+--+--+--+  +--+--+--+--+  +
|ud|        |  |u |        |   u |     |ud|ud|  |        |        |        |u |ud      |  |
+--+--+--+  +--+--+  +--+--+--+--+--+--+--+--+--+--+--+  +  +--+--+--+--+  +--+--+--+--+  +
|      ud|     |u |  |ud      |ud      |u |      ud|u |  |  |ud|      ud|  |u |      ud|  |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 2

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|u | d|     |ud|    d|  |u   d   |  |ud| d|     | d u    | d|  |u | d|  | d u    | d|  |u |
+--+--+  +--+--+--+--+  +--+--+--+  +--+--+  +--+--+--+--+--+  +--+--+  +--+--+--+--+  +  +
|        | d|ud|  |  |        |u |  |        | d| d|      ud|        |  | d u    |  |  | d|
+--+--+  +--+--+  +  +--+  +--+--+  +--+--+  +--+--+--+--+--+  +--+--+  +--+--+--+  +  +  +
| d|u |  | d   |  | d|  |  | d|        |ud|  |   u   d|  |     |  |        |        |ud|  |
+--+--+--+--+--+  +--+  +  +--+  +--+--+--+--+--+--+--+  +--+--+  +--+--+  +--+--+  +--+--+
|u |      ud|        |  |  | d|  |     |ud| d|   u   d|        |        |  |  |u |     |ud|
+--+--+--+--+  +--+--+  +--+--+--+  +--+--+--+--+--+--+  +--+--+--+  +--+--+  +--+--+--+--+
|ud|     |u |  |  |        |        | d u    | d|ud|     |  | d|  |  |        |ud      |u |
+--+--+  +--+--+  +--+--+  +--+--+  +--+--+--+--+--+--+--+  +--+  +  +--+  +--+--+--+--+--+
|  |ud|        |        |  |     |  | d u    |  |ud|        | d|  |  | d|  |    d|  |u | d|
+  +  +  +--+--+--+  +--+--+  +--+--+--+--+--+  +--+--+  +--+--+  +--+  +  +--+--+  +--+--+
| d|  |  |   u   d|  |        |ud      | d| d|        |  |u |        |  |  |ud| d|        |
+  +  +--+--+--+--+  +--+--+  +--+--+--+--+--+  +--+--+  +--+--+--+  +--+--+--+--+  +--+--+
|u |  | d|   u   d|  | d|u |  | d|   u   d|     | d|ud|  |    d u |  | d   |ud|     | d|u |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 3

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| d|  |u |    d u |  |u | d|  |u |    d u |     |u |ud|  |   u   d|  |u    |ud|     |u | d|
+  +  +--+--+--+--+  +--+--+  +--+--+--+--+--+  +--+--+  +--+--+--+  +--+--+--+--+  +--+--+
|u |  |  |    d u |  |        |ud      |u |u |        |  | d|        |  |  |ud|u |        |
+  +  +  +--+--+--+  +--+--+  +--+--+--+--+--+  +--+--+  +--+--+  +--+  +  +--+--+  +--+--+
|  |ud|        |        |  |     |  |u   d   |  |ud|        |u |  |  |u |  |   u |  | d|u |
+--+--+  +--+--+  +--+--+  +--+--+  +--+--+--+--+--+--+--+  +--+  +  +--+  +--+--+--+--+--+
|ud|     | d|  |  |        |        |u   d   |u |ud|     |  |u |  |  |        |ud      | d|
+--+--+--+--+  +--+--+  +--+--+--+  +--+--+--+--+--+--+  +--+--+--+  +--+--+  +--+--+--+--+
| d|      ud|        |  |  |u |  |     |ud|u |    d u |        |        |  |  | d|     |ud|
+--+--+--+--+--+  +--+  +  +--+  +--+--+--+--+--+--+--+  +--+--+  +--+--+  +--+--+  +--+--+
|u | d|  |u    |  |u |  |  |u |        |ud|  |    d u |  |     |  |        |        |ud|  |
+--+--+  +--+--+  +  +--+  +--+--+  +--+--+  +--+--+--+--+--+  +--+--+  +--+--+--+  +  +  +
|        |u |ud|  |  |        | d|  |        |u |u |      ud|        |  |u   d   |  |  |u |
+--+--+  +--+--+--+--+  +--+--+--+  +--+--+  +--+--+--+--+--+  +--+--+  +--+--+--+--+  +  +
| d|u |     |ud|   u |  | d u    |  |ud|u |     |u   d   |u |  | d|u |  |u   d   |u |  | d|
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 4

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|      ud|     | d|  |ud      |ud      | d|      ud| d|  |  |ud|      ud|  | d|      ud|  |
+--+--+--+  +--+--+  +--+--+--+--+--+--+--+--+--+--+--+  +  +--+--+--+--+  +--+--+--+--+  +
|ud|        |  | d|        |    d|     |ud|ud|  |        |        |        | d|ud      |  |
+--+--+--+  +  +--+--+  +--+--+--+  +--+  +  +  +--+  +--+  +--+--+--+--+  +--+--+--+--+  +
|u | d|  |  |        |  |  |        | d|  |  |  | d|  |     |ud      |ud|     |ud      |ud|
+  +  +  +--+--+  +--+  +  +--+--+  +--+  +  +  +--+  +--+--+--+--+--+  +--+--+--+--+--+--+
| d|  |        |  |  |  |        |  | d|  |  |ud| d|  |      ud|     |  |  |    d|     |  |
+  +--+  +--+--+  +  +--+  +--+--+--+--+--+--+--+--+--+--+--+--+  +--+  +  +--+--+  +--+  +
|  |     | d   |  |  |     |ud      |  | d|ud|  |  | d|  |        |  |  |  |        |  | d|
+--+--+--+--+--+--+  +--+--+--+--+--+  +--+  +  +  +--+  +--+--+  +  +--+  +--+--+  +  +  +
|ud|      ud|     |ud|      ud|     |  | d|  |  |  | d|        |  |  |        |  |  | d|u |
+  +--+--+--+--+  +--+--+--+--+  +--+  +--+  +  +  +--+  +--+--+--+  +--+--+  +  +--+--+--+
|  |      ud| d|        |        |        |  |ud|ud|     | d   |        | d|  |        |ud|
+  +--+--+--+--+  +--+--+--+--+  +  +--+--+--+--+--+--+--+--+--+--+--+  +--+--+  +--+--+--+
|  |ud      | d|  |ud      |ud|  |  | d|ud      | d|      ud|      ud|  | d|     |ud      |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 5

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|     | d   |  |  |    d|  |    d|  |  |  |  |  | d   |     | d|     | d|     |     | d   |
+--+  +--+--+  +  +--+--+  +--+--+  +  +  +  +  +--+--+  +--+--+  +--+--+  +--+--+  +--+--+
| d|        |  |        |  |        |  | d| d|  |        |        |        |    d|        |
+--+  +--+--+  +--+  +--+  +--+  +--+  +--+--+  +--+--+  +--+--+  +--+--+  +--+--+  +--+--+
| d|  |  |        |  |        |  |        |        |  |  |    d|  |  | d|  |  | d|  |  | d|
+--+--+  +  +--+--+  +--+--+  +  +  +--+--+--+--+  +  +--+--+--+--+  +--+--+  +--+--+  +  +
|        |  |     |  |     |  |  |  |     |  | d|  |        | d   |        |        |  |  |
+--+  +--+--+  +--+--+  +--+--+--+--+  +--+  +  +--+  +--+--+--+--+  +--+--+  +--+--+  +--+
|  |  |        |        |    d|        |  | d|  |     |  |  |  |     |  |     |  |        |
+  +  +--+--+  +--+--+  +--+--+--+--+  +  +--+--+--+--+  +  +  +--+--+  +--+--+  +  +--+--+
| d|  |  | d|  |  | d|  |  | d   |  |  |        |        |  |        |  |        |  |  | d|
+--+--+  +--+--+  +--+--+  +--+--+  +--+--+  +--+--+  +--+  +--+  +--+  +--+  +--+--+  +--+
|        | d   |        |        |        |  | d| d|  |        |  |        |  |        | d|
+--+--+  +--+--+  +--+--+  +--+--+  +--+--+  +  +  +  +  +--+--+  +--+--+  +  +--+--+  +--+
|    d|     |     | d|     | d|     |    d|  |  |  |  |  | d   |  | d   |  |  |    d|     |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 6

...............................................................................

 *
***
**


6x12x35 by Helmut Postl
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|u |     |u  u |     |u  u |     |     |u  u |  |u  u |     |u  u |     |u  u |     |u  u |     |u  u |u |
+  +     +--+--+     +--+--+     +     +--+--+  +--+--+     +--+--+     +--+--+     +--+--+     +--+--+  +
|u |        |  |        |        |        |        |u |        |        |  |        |  |        |u |  |u |
+--+--+  +--+  +--+  +--+--+  +--+--+  +--+--+     +--+--+  +--+--+  +--+  +--+  +--+  +--+  +--+--+  +--+
|     |  |        |  |     |  |     |  |     |     |u |  |  |     |  |        |  |        |  |  |        |
+     +--+--+     +--+     +--+     +--+     +--+--+--+  +--+     +--+--+     +--+     +--+--+  +--+     +
|        |  |     |  |        |        |        |u |        |        |  |     |  |     |  |        |     |
+--+  +--+  +--+--+  +--+  +--+--+  +--+--+  +--+--+     +--+--+  +--+  +--+--+  +--+--+  +--+     +--+--+
|u |  |        |        |  |     |  |     |  |     |     |     |  |        |        |        |     |     |
+  +--+     +--+--+     +--+     +--+     +--+     +--+--+     +--+--+     +--+     +     +--+--+--+     +
|u |  |     |u |u |     |        |        |  |        |  |        |  |     |  |     |     |u |u |        |
+--+  +--+--+  +--+--+--+--+  +--+--+  +--+  +--+  +--+  +--+  +--+  +--+--+  +--+--+--+--+  +--+--+  +--+
|        |u |u |     |     |  |     |  |        |  |        |  |        |        |     |u |u |     |  |u |
+     +--+--+--+     +     +--+     +--+--+     +--+--+     +--+     +--+     +--+     +--+--+     +--+  +
|     |     |        |        |        |  |     |     |     |  |     |  |     |  |        |        |  |u |
+--+--+     +--+  +--+--+  +--+--+  +--+  +--+--+     +--+--+  +--+--+  +--+--+  +--+  +--+--+  +--+  +--+
|     |        |  |     |  |     |  |        |        |u |        |        |        |  |     |  |        |
+     +--+  +--+--+     +--+     +--+--+     +--+  +--+--+--+     +--+     +--+     +--+     +--+--+     +
|        |  |  |        |  |        |  |     |  |  |u |     |     |  |     |  |     |  |        |  |     |
+--+  +--+--+  +--+  +--+  +--+  +--+  +--+--+  +--+--+     +--+--+  +--+--+  +--+--+  +--+  +--+  +--+--+
|u |  |u |        |  |        |  |        |        |u |        |        |        |        |  |        |u |
+  +--+--+     +--+--+     +--+--+     +--+--+     +--+--+  +--+--+     +     +--+--+     +--+--+     +  +
|u |u  u |     |u  u |     |u  u |     |u  u |     |u  u |  |u  u |     |     |u  u |     |u  u |     |u |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 1

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| d|u |   ud  d|     | d ud   |u  u |   ud  d|u | d ud   |   ud  d|u  u | d ud   |u | d ud   |   ud  d| d|
+  +--+--+--+--+     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+  +
|ud|u |     |        |     |u  u |  |u  u |     |u  ud   |u  u |     |u  u |     |u  u |     |   ud u |ud|
+  +  +     +--+  +--+     +--+--+  +--+--+     +--+--+--+--+--+     +--+--+     +--+--+     +--+--+--+  +
|  |u |        |  |  |        |        |        |u  ud   |u |        |  |u |        |  |        |     |  |
+--+--+--+  +--+--+  +--+  +--+     +--+--+  +--+--+--+--+--+--+  +--+  +--+--+  +--+  +--+  +--+     +--+
|  |     |  |u |        |  |  |     |     |  |   ud u |u  u |  |  |        |  |  |        |  |        |u |
+  +     +--+  +--+     +--+  +--+--+     +--+--+--+--+--+--+  +--+     +--+  +--+--+     +--+--+  +--+--+
|ud|        |u |u |     |        |  |        |     |u  u |        |     |        |  |     |  |u |  |     |
+  +--+  +--+--+  +--+--+     +--+  +--+  +--+     +--+--+--+     +--+--+     +--+  +--+--+  +  +--+     +
| d|  |  |  | d|ud|     |     |        |  |        |u  u |  |     |     |     |        |  |ud|ud|        |
+--+  +--+  +  +  +     +--+--+--+     +--+--+  +--+--+--+  +--+--+     +--+--+--+     +  +  +  +--+  +--+
|        |ud|ud|  |        |     |     |     |  |u  u |        |  |        |     |     |ud| d|  |  |  | d|
+     +--+  +  +--+--+  +--+     +--+--+     +--+--+--+     +--+  +--+  +--+     +--+--+  +--+--+  +--+  +
|     |  |u |  |     |  |        |     |        |u  u |     |        |  |        |     |u |u |        |ud|
+--+--+  +--+--+     +--+--+  +--+     +--+  +--+--+--+--+--+--+     +--+--+  +--+     +--+  +--+     +  +
|u |        |  |        |  |  |        |  |  |u  u |u  ud   |  |     |     |  |  |        |u |  |     |  |
+--+     +--+  +--+  +--+  +--+--+  +--+  +--+--+--+--+--+--+  +--+--+     +--+  +--+  +--+--+  +--+--+--+
|  |     |        |  |        |u |  |        |u |   ud u |        |        |        |  |  |        |u |  |
+  +--+--+--+     +--+--+     +--+--+     +--+--+--+--+--+     +--+--+  +--+--+     +--+  +--+     +  +  +
|ud|u  ud   |     |u  u |     |u  u |     |u  u |   ud u |     |u  u |  |u  u |     |        |     |u |ud|
+  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+     +--+--+--+--+  +
| d| d ud   |   ud  d|u |   ud  d|u  u | d ud   |   ud  d|u | d ud   |u  u |   ud  d|     | d ud   |u | d|
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 2

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|u  ud   | d|     |u  u | d|   ud  d|u | d|   ud u | d|u  u | d|   ud  d|u | d|   ud u | d|     | d|u  u |
+--+--+--+--+     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+     +--+--+--+
| d| d|     |        |u |   ud  d|u | d ud   |u | d  d|   ud  d|u |   ud  d|u |   ud  d|        | d  d| d|
+--+  +     +--+  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+
|u |ud|        |  |     |     |u  u |     |u  u | d  d|   ud u |     |u  ud   |     |     |  |     |u |u |
+  +  +--+  +--+--+     +     +--+--+     +--+--+--+--+--+--+--+     +--+--+--+     +     +--+     +--+  +
|u |  |  |  | d|        |        |        |  |u | d  d| d ud   |        |  |        |        |        |ud|
+--+--+  +--+  +--+  +--+--+  +--+--+  +--+  +--+--+--+--+--+--+--+  +--+  +--+  +--+--+  +--+--+  +--+  +
| d|        |ud| d|  |     |  |     |  |        |u | d ud   |     |  |        |  |     |  |u | d|  |  |  |
+--+--+     +  +  +--+     +--+     +--+--+     +--+--+--+--+     +--+--+     +--+     +--+--+  +--+  +--+
|     |     |  | d|  |        |        |  |     |u | d ud   |        |  |     |  |        | d| d|        |
+     +--+--+--+--+  +--+  +--+--+  +--+  +--+--+--+--+--+--+--+  +--+  +--+--+  +--+  +--+--+--+--+     +
|        | d| d|        |  |     |  |        |   ud  d|u |     |  |        |        |  | d|  |     |     |
+--+  +--+  +--+--+     +--+     +--+--+     +--+--+--+--+     +--+--+     +--+     +--+  +  +     +--+--+
|  |  |  | d|u |  |     |  |        |  |     |   ud  d|u |        |  |     |  |     |  | d|ud|        | d|
+  +--+  +--+--+  +--+--+  +--+  +--+  +--+--+--+--+--+--+--+  +--+  +--+--+  +--+--+  +--+  +--+  +--+--+
|ud|        |        |        |  |        |   ud  d| d  d|u |  |        |        |        | d|  |  |  |u |
+  +--+     +--+     +     +--+--+--+     +--+--+--+--+--+--+--+     +--+--+     +     +--+--+  +--+  +  +
|u |u |     |  |     |     |   ud u |     |u  ud   | d  d|u  u |     |u  u |     |     |  |        |ud|u |
+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+  +--+     +  +--+
| d| d  d|        | d ud   |u | d ud   |u | d ud   | d  d|u |   ud  d|u | d ud   |u |        |     | d| d|
+--+--+--+     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+     +--+--+--+--+
|u  u | d|     | d|u  ud   | d|u | d ud   | d|u  u | d|u  ud   | d|u | d ud   | d|u  u |     | d|   ud u |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 3

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| d  d|u |     |u | d ud   |u | d|u  ud   |u | d  d|u | d ud   |u | d|u  ud   |u | d  d|     |u |   ud  d|
+--+--+--+     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+     +--+--+--+--+
|u |u  u |        |u  ud   | d|u  ud   | d|u  ud   |u  u | d|   ud u | d|u  ud   | d|        |     |u |u |
+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+  +--+     +  +--+
| d| d|     |  |     |     |   ud  d|     | d ud   |u  u | d  d|     | d  d|     |     |  |        |ud| d|
+  +--+     +--+     +     +--+--+--+     +--+--+--+--+--+--+--+     +--+--+     +     +--+--+  +--+  +  +
|ud|        |        |        |  |        |   ud u |u  u | d|  |        |        |        |u |  |  |  | d|
+  +--+  +--+--+  +--+--+  +--+  +--+  +--+--+--+--+--+--+--+  +--+  +--+--+  +--+--+  +--+  +--+  +--+--+
|  |  |  |u | d|  |     |  |        |  |     |   ud u | d|        |  |     |  |     |  |u |ud|        |u |
+--+  +--+  +--+--+     +--+     +--+--+     +--+--+--+--+     +--+--+     +--+     +--+  +  +     +--+--+
|        |u |u |        |  |     |  |        |   ud u | d|     |  |        |        |  |u |  |     |     |
+     +--+--+--+--+  +--+  +--+--+  +--+  +--+--+--+--+--+--+--+  +--+  +--+--+  +--+  +--+--+--+--+     +
|     |     |  |u |  |        |        |  |     | d|u  ud   |        |  |     |  |        |u |u |        |
+--+--+     +  +  +--+     +--+     +--+--+     +--+--+--+--+     +--+--+     +--+     +--+--+  +--+  +--+
|u |        |ud|u |  |     |  |     |  |        | d|u  ud   |     |  |        |  |     |  | d|u |  |  |  |
+--+--+  +--+  +--+  +--+--+  +--+--+  +--+  +--+--+--+--+--+--+--+  +--+  +--+  +--+--+  +--+--+  +--+  +
| d|  |  |  |u |        |        |        |  | d|u  u |u  ud   |        |  |        |        |        |ud|
+  +  +--+  +--+--+     +     +--+--+     +--+--+--+--+--+--+--+     +--+--+--+     +     +--+     +--+  +
| d|ud|        |  |     |     | d  d|     | d  d|u  u |   ud  d|     | d ud   |     |     |  |     | d| d|
+--+  +     +--+  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+
|u |u |     |        | d|   ud u | d|u  ud   | d|u  u |   ud u | d|   ud u | d|   ud u |        |u  u |u |
+--+--+--+--+     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+     +--+--+--+
| d ud   |u |     | d  d|u |   ud u | d|u |   ud  d|u | d  d|u |   ud u | d|u |   ud  d|u |     |u | d  d|
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 4

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|u |u  ud   |   ud u | d|   ud u | d  d|u  ud   |   ud u | d|u  ud   | d  d|   ud u |     |u  ud   | d|u |
+  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+     +--+--+--+--+  +
|ud| d ud   |     | d  d|     | d  d|     | d  d|   ud  d|     | d  d|  | d  d|     |        |     | d|ud|
+  +--+--+--+     +--+--+     +--+--+     +--+--+--+--+--+     +--+--+  +--+--+     +--+  +--+     +  +  +
|  |     |        |  |        | d|  |        | d|   ud  d|        |        |        |  |  |        | d|  |
+--+     +--+  +--+  +--+  +--+--+  +--+  +--+--+--+--+--+--+  +--+--+     +--+  +--+  +--+--+  +--+--+--+
| d|        |  |        |  |  |        |  |  | d  d| d ud   |  |     |     |  |  |        | d|  |     |  |
+--+--+  +--+--+     +--+--+  +--+     +--+  +--+--+--+--+--+--+     +--+--+  +--+     +--+  +--+     +  +
|     |  | d|  |     |  |        |     |        | d  d|     |        |  |        |     | d| d|        |ud|
+     +--+  +  +--+--+  +--+     +--+--+     +--+--+--+     +--+  +--+  +--+     +--+--+  +--+--+  +--+  +
|        |ud|ud|  |        |     |     |     |  | d  d|        |  |        |     |     |ud|u |  |  |  |u |
+--+  +--+  +  +  +     +--+--+--+     +--+--+  +--+--+--+  +--+--+     +--+--+--+     +  +  +  +--+  +--+
|u |  |  |  |u |ud|     |     |        |  |        | d  d|  |     |     |     |        |  |ud|ud|        |
+  +--+  +--+--+  +--+--+     +--+  +--+  +--+     +--+--+--+     +--+--+     +--+  +--+--+  +  +--+     +
|ud|        | d| d|     |        |  |        |     | d  d|        |     |        |  |     |  | d|  |     |
+  +     +--+  +--+     +--+  +--+--+     +--+--+--+--+--+--+  +--+     +--+  +--+--+     +--+--+  +--+--+
|  |     |  | d|        |  |  |     |     |  |   ud  d| d  d|  |  |        |  |  |        |  |        | d|
+--+--+--+  +--+--+  +--+  +--+     +--+--+  +--+--+--+--+--+--+  +--+  +--+--+  +--+  +--+  +--+     +--+
|  | d|        |  |  |        |        |        | d ud   | d|        |  | d|        |  |        |     |  |
+  +  +     +--+  +--+     +--+--+  +--+--+     +--+--+--+--+--+     +--+--+     +--+--+     +--+--+--+  +
|ud| d|     |        |     | d  d|  | d  d|     | d ud   | d  d|     | d  d|     | d  d|     |   ud  d|ud|
+  +--+--+--+--+     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+  +
|u | d|   ud u |     |u  ud   | d  d|   ud u | d|u  ud   |   ud u | d  d|u  ud   | d|u  ud   |   ud u |u |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 5

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| d| d  d|     | d  d|     | d  d|     | d  d|     | d  d|  | d  d|     |     | d  d|     | d  d|     | d|
+  +--+--+     +--+--+     +--+--+     +--+--+     +--+--+  +--+--+     +     +--+--+     +--+--+     +  +
| d|  | d|        |  |        |  |        |        | d|        |        |        |        |  |        | d|
+--+  +--+--+  +--+  +--+  +--+  +--+  +--+--+  +--+--+     +--+--+  +--+--+  +--+--+  +--+  +--+  +--+--+
|        |  |  |        |  |        |  |     |  |  | d|     |     |  |     |  |     |  |        |  |     |
+     +--+  +--+--+     +--+     +--+--+     +--+  +--+--+--+     +--+     +--+     +--+     +--+--+     +
|     |        |  |     |  |     |  |        |        | d|        |        |        |  |     |  |        |
+--+--+     +--+  +--+--+  +--+--+  +--+  +--+--+     +--+--+  +--+--+  +--+--+  +--+  +--+--+  +--+  +--+
|     |     |        |        |        |  |     |     |     |  |     |  |     |  |        |        |  | d|
+     +--+--+--+     +     +--+     +--+--+     +--+--+     +--+     +--+     +--+     +--+--+     +--+  +
|        | d| d|     |     |  |     |  |        |  |        |  |        |        |     | d| d|     |  | d|
+--+  +--+--+  +--+--+--+--+  +--+--+  +--+  +--+  +--+  +--+  +--+  +--+--+  +--+--+--+--+  +--+--+  +--+
| d|  |     | d| d|     |        |        |  |        |  |        |  |     |  |     |     | d| d|        |
+  +--+     +--+--+     +--+     +--+     +--+     +--+--+     +--+--+     +--+     +     +--+--+--+     +
| d|  |        |        |  |     |  |     |  |     |     |     |  |        |        |        |     |     |
+--+  +--+  +--+--+  +--+  +--+--+  +--+--+  +--+--+     +--+--+  +--+  +--+--+  +--+--+  +--+     +--+--+
|        |  |     |  |        |        |        | d|        |        |  |     |  |     |  |        |     |
+     +--+--+     +--+     +--+     +--+     +--+--+--+  +--+     +--+--+     +--+     +--+--+  +--+     +
|     |  |        |  |     |  |     |  |     |     | d|  |  |     |  |        |  |        |  |  |        |
+--+--+  +--+  +--+  +--+--+  +--+--+  +--+--+     +--+--+  +--+--+  +--+  +--+  +--+  +--+  +--+--+  +--+
| d|        |  |        |        |        |        | d|        |        |  |        |  |        | d|  | d|
+  +     +--+--+     +--+--+     +     +--+--+  +--+--+     +--+--+     +--+--+     +--+--+     +--+--+  +
| d|     | d  d|     | d  d|     |     | d  d|  | d  d|     | d  d|     | d  d|     | d  d|     | d  d| d|
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
level 6

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***
  **


6x8x60 by Helmut Postl

...............................................................................

*
****
 *


6x10x56 by Helmut Postl

...............................................................................

2*
***


2x2x3 minimal
+--+--+--+  +--+--+--+
|u    |u |  | d|    d|
+     +--+  +--+     +
|        |  |        |
+--+--+--+  +--+--+--+
level 1      level 2

...............................................................................

**
**2


2x2x3 minimal
+--+--+--+  +--+--+--+
|     |u |  |       d|
+     +--+  +     +--+
|      u |  |     | d|
+--+--+--+  +--+--+--+
level 1      level 2

also: 2x5x15, 2x7x9, 3x4x5, 3x5x10, 3x6x7, 5x5x6
allowing reflections: also 2x3x9, 3x3x8, 3x3x12, 3x3x14, 3x3x18, 3x5x6

...............................................................................

2*
 *2


2x2x3 minimal
+--+--+--+  +--+--+--+
|u    |u |  | d|    d|
+--+  +--+  +--+  +--+
|u |   u |  | d   | d|
+--+--+--+  +--+--+--+
level 1      level 2

...............................................................................

*2*
* *


2x2x3 minimal
+--+--+--+  +--+--+--+
|   u    |  |  | d|  |
+  +--+  +  +  +--+  +
|  |u |  |  |    d   |
+--+--+--+  +--+--+--+
level 1      level 2

also: 3x5x8, 3x5x12

...............................................................................

22
**


2x2x3 minimal
+--+--+--+  +--+--+--+
|u    |u |  | d|    d|
+     +  +  +  +     +
|u    |u |  | d|    d|
+--+--+--+  +--+--+--+
level 1      level 2

also: 2x5x9, 6x7x7

...............................................................................

2*
*2


2x2x3 minimal
+--+--+--+  +--+--+--+
|u |   u |  | d   | d|
+  +--+  +  +  +--+  +
|u    |u |  | d|    d|
+--+--+--+  +--+--+--+
level 1      level 2

...............................................................................

2
*3


2x2x3 minimal
+--+--+--+  +--+--+--+
|        |  |        |
+  +--+--+  +--+--+  +
|u |   u |  | d   | d|
+--+--+--+  +--+--+--+
level 1      level 2

...............................................................................

**
2**


2x3x4 minimal
+--+--+--+--+  +--+--+--+--+
|u |      u |  | d      | d|
+--+--+     +  +     +--+--+
|     |     |  |     |     |
+     +--+--+  +--+--+     +
|u       |u |  | d|       d|
+--+--+--+--+  +--+--+--+--+
level 1         level 2


same hexacube, allowing reflections


2x2x3 minimal
+--+--+--+  +--+--+--+
|     |u |  |       d|
+     +--+  +--+     +
|u       |  | d|     |
+--+--+--+  +--+--+--+
level 1      level 2

...............................................................................

* *
**2


2x3x4 minimal
+--+--+--+--+  +--+--+--+--+
|u |      u |  | d      | d|
+--+  +--+  +  +  +--+  +--+
|  |  |  |  |  |  |  |  |  |
+  +--+  +--+  +--+  +--+  +
|u       |u |  | d|       d|
+--+--+--+--+  +--+--+--+--+
level 1         level 2

...............................................................................

2
*2*


2x3x4 minimal
+--+--+--+--+  +--+--+--+--+
|u       |u |  | d|       d|
+--+  +--+  +  +  +--+  +--+
|  |  |  |  |  |  |  |  |  |
+  +--+  +--+  +--+  +--+  +
|u |      u |  | d      | d|
+--+--+--+--+  +--+--+--+--+
level 1         level 2

...............................................................................

2
**2


2x3x4 minimal
+--+--+--+--+  +--+--+--+--+
|u       |u |  | d|       d|
+--+--+  +  +  +  +  +--+--+
|  |  |  |  |  |  |  |  |  |
+  +  +--+--+  +--+--+  +  +
|u |      u |  | d      | d|
+--+--+--+--+  +--+--+--+--+
level 1         level 2

also: 2x5x12

...............................................................................

**
 **2


2x3x4 minimal
+--+--+--+--+  +--+--+--+--+
|u       |u |  | d|       d|
+--+--+  +--+  +--+  +--+--+
|     |     |  |     |     |
+--+  +--+--+  +--+--+  +--+
|u |      u |  | d      | d|
+--+--+--+--+  +--+--+--+--+
level 1         level 2

...............................................................................

2
**
 **


2x3x4 minimal
+--+--+--+--+  +--+--+--+--+
|u |     |u |  | d|     | d|
+  +--+  +--+  +--+  +--+  +
|     |     |  |     |     |
+--+  +--+  +  +  +--+  +--+
|u |     |u |  | d|     | d|
+--+--+--+--+  +--+--+--+--+
level 1         level 2

...............................................................................

*2
***


+--+        +--+
|u |        | d|
+  +--+     +  +--+
|u    |     | d|  |
+--+--+--+  +  +  +--+
|   u  u |  |  | d  d|
+--+--+--+  +--+--+--+
level 1      level 2


2x3x4 minimal
+--+--+--+--+
|  |        |
+  +--+     +
|     |     |
+     +--+  +
|        |  |
+--+--+--+--+
(2 levels deep)

...............................................................................

**
*2*


+--+        +--+
|u |        | d|
+  +--+     +  +--+
|u    |     | d|  |
+  +--+--+  +--+  +--+
|  |u  u |  |    d  d|
+--+--+--+  +--+--+--+
level 1      level 2


2x3x4 minimal
+--+--+--+--+
|  |        |
+  +--+     +
|     |     |
+     +--+  +
|        |  |
+--+--+--+--+
(2 levels deep)

...............................................................................

*
*2**


2x2x6 minimal
+--+--+--+--+--+--+  +--+--+--+--+--+--+
|  |u |      u    |  |    d      | d|  |
+  +--+--+--+--+  +  +  +--+--+--+--+  +
|   u       |u |  |  |  | d|       d   |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2

...............................................................................

2*
 ***


2x2x6 minimal
+--+--+--+--+--+--+  +--+--+--+--+--+--+
|u    |        |u |  | d|        |    d|
+--+  +--+--+  +--+  +--+  +--+--+  +--+
|u |        |   u |  | d   |        | d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2

...............................................................................

* 2
***


+--+     +--+     +--+     +--+
|  |     |u |     |ud|     | d|
+  +--+  +  +--+  +--+--+  +  +--+
|   u |  |  |ud|  |    d|  |     |
+--+--+  +--+--+  +--+--+  +--+--+
level 1  level 2  level 3  level 4


2x3x4 minimal
+--+--+--+
|  |     |
+  +--+  +
|     |  |
+--+--+--+
(4 levels deep)

also: 4x5x9

...............................................................................

2
2**


2x3x4 minimal
+--+--+--+--+  +--+--+--+--+
|u       |u |  | d|  |  | d|
+  +--+--+  +  +  +  +  +  +
|u |      u |  | d|  |  | d|
+--+--+--+--+  +--+  +  +--+
|u  u |u  u |  | d  d| d  d|
+--+--+--+--+  +--+--+--+--+
level 1         level 2

also: 2x6x6 by Torsten Sillke
also: 2x6x17, 2x7x18, 2x9x22, 2x10x15, 3x5x12, 3x5x14, 3x5x16, 3x5x18,
      3x5x20, 3x5x22, 3x6x9, 3x6x10, 3x6x11, 3x7x8, 3x7x10, 3x7x14, 3x9x10,
      4x5x9, 5x5x6, 5x6x6, 5x6x7, 6x7x7

...............................................................................

  2
****


   +--+--+        +--+--+
   |u |u |        | d| d|
+--+--+  +--+  +--+  +--+--+
|           |  |           |
+--+--+--+--+  +--+--+--+--+
level 1         level 2


2x4x6 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+
|  |           |  |
+  +--+     +--+  +
|     |     |     |
+     +--+--+     +
|     |     |     |
+  +--+     +--+  +
|  |           |  |
+--+--+--+--+--+--+
(2 levels deep)

also: 2x5x12

...............................................................................

 2
2**


   +--+--+        +--+--+
   |u |u |        | d| d|
+--+  +--+--+  +--+--+  +--+
|u       |u |  | d|       d|
+--+--+--+--+  +--+--+--+--+
level 1         level 2


2x4x6 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+
|  |           |  |
+  +--+     +--+  +
|     |     |     |
+     +--+--+     +
|     |     |     |
+  +--+     +--+  +
|  |           |  |
+--+--+--+--+--+--+
(2 levels deep)

also: 2x5x12

...............................................................................

 **
22


   +--+--+        +--+--+
   |     |        |     |
+--+  +--+--+  +--+--+  +--+
|u  u |u  u |  | d  d| d  d|
+--+--+--+--+  +--+--+--+--+
level 1         level 2


2x4x6 minimal
+--+--+--+--+--+--+
|  |           |  |
+  +--+     +--+  +
|     |     |     |
+     +--+--+     +
|     |     |     |
+  +--+     +--+  +
|  |           |  |
+--+--+--+--+--+--+
(2 levels deep)

also: 2x5x12

...............................................................................

   2
****


+--+     +--+  +--+     +--+
|u |     |u |  | d|     | d|
+--+--+--+  +  +  +--+--+--+
|           |  |           |
+--+--+--+--+  +--+--+--+--+
level 1         level 2


   +--+--+        +--+--+
   |   u |        |  | d|
+--+--+--+--+  +--+  +  +--+
|         u |  |  |  |  | d|
+--+--+--+--+  +  +  +  +  +
|u          |  | d|  |  |  |
+--+--+--+--+  +--+  +  +--+
   |u    |        | d|  |
   +--+--+        +--+--+
level 1         level 2


2x4x6 minimal
+--+--+--+--+--+--+
|     |     |     |
+  +--+     +--+  +
|  |           |  |
+  +           +  +
|  |           |  |
+  +--+     +--+  +
|     |     |     |
+--+--+--+--+--+--+
(2 levels deep)

also: 6x6x6 by Torsten Sillke


same hexacube, allowing reflections


2x3x6 minimal
+--+--+--+--+--+--+  +--+--+--+--+--+--+
|u          |u |u |  | d|          d| d|
+--+--+--+--+  +--+  +  +--+--+--+--+  +
|           |  |  |  |  |  |           |
+  +--+--+--+--+  +  +--+  +--+--+--+--+
|u |u          |u |  | d| d|          d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2

...............................................................................

***
  3


3x4x4 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|u       |u |  | d|       d|  |  |        |
+--+--+--+  +  +  +--+--+--+  +  +  +--+--+
|  |u |u |  |  |  |ud|ud|  |  |  | d| d   |
+  +--+--+  +  +  +--+--+  +  +  +--+--+  +
|  |u |u |  |  |  |ud|ud|  |  |    d| d|  |
+  +--+--+--+  +--+--+--+  +  +--+--+  +  +
|u |      u |  | d      | d|  |        |  |
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3


also: 6x6x6 (allowing reflections) by Torsten Sillke

...............................................................................

          _________
         /        /\
        /________/  \
        \        \  /
  _______\________\/
 /           /   /
/___________/   /
\           \  /
 \___________\/


2x4x6 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+  +--+--+--+--+--+--+
|      u |u |  |  |  |  |  | d| d      |
+--+--+--+  +  +  +  +  +  +  +--+--+--+
|u    |     |  |u |  | d|  |     |    d|
+--+  +--+--+  +--+  +--+  +--+--+  +--+
|u |  |     |   u |  | d   |     |  | d|
+  +  +  +--+--+--+  +--+--+--+  +  +  +
|  |  |u |u       |  |       d| d|  |  |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2

...............................................................................

 2**
**


2x4x6 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+  +--+--+--+--+--+--+
|   u |      u |  |  |  | d      | d   |
+--+--+--+--+  +  +  +  +  +--+--+--+--+
|      u |  |  |u |  |  |  | d   |    d|
+--+--+  +  +--+--+  +  +--+--+--+--+  +
|u |  |  |u       |  | d   |    d|  |  |
+  +  +--+--+--+--+  +--+--+--+--+  +  +
|  |u       |u    |  |    d|       d|  |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2


...............................................................................

***2
*

allowing reflections


2x6x6 minimal by Torsten Sillke
+--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |         u |u |  | d         | d| d|
+--+  +--+--+--+  +  +--+--+--+  +--+--+
|u |  |u |     |  |  | d|  | d|  |     |
+--+--+  +  +--+  +  +  +  +--+--+--+  +
|     |  |  |u |  |  |  |          d|  |
+  +--+  +  +--+  +  +  +--+--+--+--+  +
|  |u |  |  |     |  |  | d         |  |
+  +--+  +  +--+--+  +  +--+--+--+  +  +
|  |     |u |  |u |  |     |  | d|  | d|
+  +--+--+--+  +--+  +--+--+  +--+--+--+
|u |u          |u |  | d| d|          d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2

...............................................................................

2**
*
*


4x4x6 minimal by Helmut Postl
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|u       |u |  | d|       d|  |u       |u |  | d|       d|
+  +--+--+--+  +--+--+--+  +  +  +--+--+--+  +--+--+--+  +
|  |u       |  |  |ud|u |  |  |  | d|ud|  |  |       d|  |
+  +  +--+--+  +  +--+--+  +  +  +--+--+  +  +--+--+  +  +
|  |  |u    |  |  |u |ud|  |  |  |ud| d|  |  |    d|  |  |
+--+--+  +--+  +  +--+--+--+  +--+--+--+  +  +--+  +--+--+
|u |  |  |  |  | d      |  |  |  |      u |  |  |  |  | d|
+--+  +  +  +  +--+--+--+  +  +  +--+--+--+  +  +  +  +--+
|u |  |  |  |  |ud|      u |  | d      |ud|  |  |  |  | d|
+--+  +--+  +  +--+--+--+--+  +--+--+--+--+  +  +--+  +--+
|   u |   u |  |u |ud|u |ud|  |ud| d|ud| d|  | d   | d   |
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4

...............................................................................

3*
 **


4x4x6 minimal by Helmut Postl
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|u    |u    |  |ud|    d|u |  | d|u    |ud|  |    d|    d|
+--+  +--+  +  +--+--+--+--+  +--+--+--+--+  +  +--+  +--+
|u |     |  |  | d u |u |  |  |  | d| d u |  |  |     | d|
+--+--+--+  +  +--+--+  +  +  +  +  +--+--+  +  +--+--+--+
|  |u    |  |  |    d|  |  |  |  |  |u    |  |  |    d|  |
+  +--+  +--+  +--+--+  +  +  +  +  +--+--+  +--+  +--+  +
|  |u |  |  |  |u   d|  |u |  | d|  |u   d|  |  |  | d|  |
+  +--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+  +
|   u |  |  |  |u | d   |u |  | d|   u | d|  |  |  | d   |
+--+--+--+  +  +  +--+--+--+  +--+--+--+  +  +  +--+--+--+
|u       |u |  | d|u |u   d|  |u   d| d|u |  | d|       d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4


same hexacube, allowing reflections

3x4x6 minimal
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|u |u    |u |  |ud|ud|u   d|  | d| d| d|  |
+--+--+  +--+  +--+--+--+--+  +  +--+  +  +
|   u |     |  |  | d   |u |  |     |  | d|
+  +--+--+--+  +  +--+--+  +  +--+  +  +--+
|  |        |  |u |        |  | d|  |  |  |
+  +--+--+  +  +--+--+--+--+  +  +--+--+  +
|  |  |  |u |  |        | d|  |        |  |
+--+  +  +--+  +  +--+--+  +  +--+--+--+  +
|u |  |     |  | d|   u |  |  |     | d   |
+  +  +--+  +  +--+--+--+--+  +--+  +--+--+
|  |u |u |u |  |u   d|ud|ud|  | d|    d| d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3

...............................................................................

**2*
*


      +--+              +--+
      |  |              |  |
+--+--+  +--+--+  +--+--+  +--+--+
|u          |u |  | d|          d|
+--+--+--+--+--+  +--+--+--+--+--+
level 1            level 2


+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|         u |  |  |     | d|  |u |     |  |  | d         |
+--+  +--+--+  +  +  +--+--+  +--+--+  +  +  +--+--+  +--+
|u |  |   u |  |ud|  |  |ud|  |ud|  |  |ud|  | d   |  | d|
+--+--+--+--+  +--+  +  +--+  +--+  +  +--+  +--+--+--+--+
   |u |u |        | d| d|        |u |u |        | d| d|
+--+--+--+--+  +--+  +  +--+  +--+  +  +--+  +--+--+--+--+
|u    |  |u |  |ud|  |  |ud|  |ud|  |  |ud|  | d|  |    d|
+--+--+  +--+  +--+--+  +  +  +  +  +--+--+  +--+  +--+--+
|u          |  | d|     |  |  |  |     |u |  |          d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4


4x5x6 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+
|  |           |  |
+  +           +  +
|  |           |  |
+  +--+     +--+  +
|     |     |     |
+  +--+     +--+  +
|  |           |  |
+  +           +  +
|  |           |  |
+--+--+--+--+--+--+
(4 levels deep)

...............................................................................

*2**
 *


4x6x6 minimal by Helmut Postl
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |  |u |u |  |u |  |ud   |ud|ud|   ud|  |ud|   ud|ud   |ud|  | d|  | d| d|  | d|
+--+  +--+--+  +--+  +  +--+--+--+--+  +  +--+--+  +  +--+--+  +--+  +--+--+  +--+
|   u       |u    |  |  | d|  |  | d|  |  |  |u |  |  |u |  |  |    d      | d   |
+--+--+--+--+  +--+  +--+--+  +  +--+--+  +  +--+--+--+--+  +  +--+--+--+--+  +--+
|u |  |u |u |  |u |  |ud|   ud|ud   |ud|  |ud   |ud|ud|   ud|  | d|  | d| d|  | d|
+--+  +--+--+  +--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+  +--+--+  +--+
|u |  |u |u |  |u |  |ud|   ud|ud   |ud|  |ud   |ud|ud|   ud|  | d|  | d| d|  | d|
+--+  +--+--+--+--+  +--+--+  +  +--+--+  +  +--+--+--+--+  +  +--+  +--+--+--+--+
|   u |      u    |  |  | d|  |  | d|  |  |  |u |  |  |u |  |  |    d|       d   |
+--+  +--+--+  +--+  +  +--+--+--+--+  +  +--+--+  +  +--+--+  +--+  +--+--+  +--+
|u |  |u |u |  |u |  |ud   |ud|ud|   ud|  |ud|   ud|ud   |ud|  | d|  | d| d|  | d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4

...............................................................................

        ____
       /   /\
  ____/___/  \
 /   /\   \   \
/___/  \___\   \
\   \  /   /   /
 \   \/___/   /
  \       \   \
   \____   \   \
        \   \  /
         \___\/


2x7x12 minimal by Helmut Postl
+--+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+--+
|  |u    |u    |   u |   u |   u |  |  |    d|    d|     | d   | d   | d   |
+  +--+--+  +--+--+--+--+  +--+--+  +  +--+  +--+--+  +--+  +--+--+--+  +--+
|u    |     |u    |   u |     |   u |  | d|     |    d|     | d   |     | d|
+--+  +--+--+--+--+--+--+--+--+  +--+  +  +--+--+--+--+--+--+  +--+--+--+  +
|  |  |  |u    |u    |   u |  |  |  |  |  |  |    d|    d|     | d   |  |  |
+  +--+  +--+--+--+--+--+--+  +--+  +  +--+  +--+  +--+  +--+--+  +--+  +--+
|u    |u |     |     |     |u    |u |  | d|    d|     |     |     | d|    d|
+--+  +--+  +--+--+  +--+  +--+  +--+  +  +--+  +--+--+--+--+--+--+  +--+  +
|  |  |   u |     |u    |u    |  |  |  |  |  |  | d   |    d|    d|  |  |  |
+  +--+--+--+  +--+--+--+--+--+--+  +  +--+  +--+--+--+--+--+--+--+--+  +--+
|u |     |   u |     |u    |     |u |  | d   |     | d   |    d|     |    d|
+--+  +--+--+--+  +--+  +--+--+  +--+  +  +--+--+  +--+--+--+--+  +--+--+  +
|   u |   u |   u |     |u    |u    |  |  | d   | d   | d   |    d|    d|  |
+--+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+--+
level 1                                 level 2

...............................................................................

  **
*2*


4x4x12 minimal by Patrick Hamlyn
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|u |   u    |  |ud   | d|u |  | d|u |   ud|  |    d   | d|
+--+  +--+--+  +--+--+--+  +  +  +--+--+--+  +--+--+  +--+
|     |  |u |  |  |  |  | d|  |u |  |  |  |  | d|  |     |
+--+--+  +--+  +  +  +  +--+  +--+  +  +  +  +--+  +--+--+
|u |u |     |  | d| d|     |  |     |u |u |  |     | d| d|
+  +--+--+  +  +--+  +  +--+  +--+  +  +--+  +  +--+--+  +
|     |u |u |  |     | d| d|  |u |u |     |  | d| d|     |
+  +--+  +  +  +  +--+--+--+  +--+--+--+  +  +  +  +--+  +
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
+--+  +--+--+  +--+  +  +  +  +  +  +  +--+  +--+--+  +--+
|     |u |u |  |     | d| d|  |u |u |     |  | d| d|     |
+--+  +  +--+  +  +--+--+  +  +  +--+--+  +  +--+  +  +--+
|u |u |     |  | d| d|     |  |     |u |u |  |     | d| d|
+--+--+  +--+  +  +  +  +--+  +--+  +  +  +  +--+  +--+--+
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
+  +  +--+  +  +--+--+--+  +  +  +--+--+--+  +  +--+  +  +
|u |u |     |  | d| d|     |  |     |u |u |  |     | d| d|
+  +--+--+  +  +--+  +  +--+  +--+  +  +--+  +  +--+--+  +
|     |u |u |  |     | d| d|  |u |u |     |  | d| d|     |
+--+  +--+--+  +--+  +  +  +  +  +  +  +--+  +--+--+  +--+
|u |  |     |  | d|  |  |  |  |  |  |  |u |  |     |  | d|
+--+--+  +--+  +  +--+--+--+  +--+--+--+  +  +--+  +--+--+
|   u    |u |  |u | d|   ud|  |ud   |u | d|  | d|    d   |
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4


same hexacube, allowing reflections

4x4x6 minimal
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|u |   u    |  |ud   | d|u |  | d|u |   ud|  |    d   | d|
+--+  +--+--+  +--+--+--+  +  +  +--+--+--+  +--+--+  +--+
|     |  |u |  |  |  |  | d|  |u |  |  |  |  | d|  |     |
+--+--+  +--+  +  +  +  +--+  +--+  +  +  +  +--+  +--+--+
|u |u |     |  | d| d|     |  |     |u |u |  |     | d| d|
+--+  +  +--+  +  +--+--+  +  +  +--+--+  +  +--+  +  +--+
|     |u |u |  |     | d| d|  |u |u |     |  | d| d|     |
+--+  +--+--+  +--+  +  +  +  +  +  +  +--+  +--+--+  +--+
|u |  |     |  | d|  |  |  |  |  |  |  |u |  |     |  | d|
+--+--+  +--+  +  +--+--+--+  +--+--+--+  +  +--+  +--+--+
|   u    |u |  |u | d|   ud|  |ud   |u | d|  | d|    d   |
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4


...............................................................................

 3
***


6x7x8 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|u |  |  |u |   u    |  |ud   |   ud|  | d|  |  | d|u |  | d|   u    |
+--+  +  +--+--+--+--+  +--+  +  +--+  +  +  +  +--+  +  +--+--+--+--+
|u    |   u |      u |  |ud|  |  |ud|  |  | d|  | d|  |u | d|u       |
+--+  +  +--+--+--+--+  +--+  +  +--+  +  +  +  +--+  +  +--+--+--+--+
|u |  |  |   u    |  |  |ud|  |  |u | d|  |  |  | d|  |  |ud|        |
+--+--+--+--+--+--+  +  +  +--+--+--+--+--+--+  +--+--+--+  +--+--+  +
|  |        |u |u    |  |        |  |ud|ud|u |  |u |        | d| d|ud|
+  +--+  +--+--+--+  +  +--+--+--+  +--+--+--+  +--+--+--+--+  +--+--+
|   u |u |u       |  |  |u |ud|ud| d|        |  |ud| d| d|        |u |
+  +--+--+--+--+--+--+  +--+--+--+  +--+--+  +  +  +--+--+--+--+--+--+
|  |   u    |  |  |u |  |  |  | d|  |  |  |ud|  |        |u |  |  | d|
+--+--+--+--+  +  +--+  +  +  +  +--+  +  +--+  +--+--+--+--+  +  +--+
|u       |u    |   u |  | d|  |  |ud|  |  |ud|  |      u | d|u |  | d|
+--+--+--+--+  +  +--+  +  +  +  +--+  +  +--+  +--+--+--+--+  +  +--+
|   u    |u |  |  |u |  |  | d|  |ud   |   ud|  |   u    | d|  |u | d|
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2                 level 3

+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|    d   |u |  | d|u |  |  |u |  |ud   |   ud|  |    d   | d|  |  | d|
+--+--+--+--+  +  +--+  +  +  +  +--+  +  +--+  +--+--+--+--+  +  +--+
|       d|u | d|  |u |  |u |  |  |ud|  |  |ud|  | d      | d   |    d|
+--+--+--+--+  +  +--+  +  +  +  +--+  +  +--+  +--+--+--+--+  +  +--+
|        | d|  |  |u |  |  |  |u |  |  |  |ud|  |  |    d   |  |  | d|
+  +--+--+--+--+--+--+  +--+--+--+  +--+--+  +  +  +--+--+--+--+--+--+
|ud|u |u |        | d|  | d|ud|ud|u |        |  |    d| d| d      |  |
+--+--+--+--+  +--+--+  +--+--+--+  +--+--+--+  +  +--+  +--+--+--+  +
| d|        |u |u |ud|  |        |  |ud|ud| d|  |  |        | d| d   |
+--+--+--+  +--+--+  +  +  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +
|u |  |  |ud|        |  |ud|  |  | d|u |  |  |  | d|  |  |    d   |  |
+--+  +  +--+--+--+--+  +--+  +  +--+  +  +  +  +--+  +  +--+--+--+--+
|u |  | d|u | d      |  |ud|  |  |ud|  |  |u |  | d   |    d|       d|
+--+  +  +--+--+--+--+  +--+  +  +--+  +  +  +  +--+  +  +--+--+--+--+
|u | d|  |u |    d   |  |ud   |   ud|  |u |  |  | d|  |  | d|    d   |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
 level 4                 level 5                 level 6


also: 4x8x12 by Helmut Postl
also: 4x9x14, 4x9x15, 4x9x22,
      5x6x56, 5x6x58, 5x6x60, 5x6x64, 5x6x66, 5x6x68, 5x6x70, 5x6x72, 5x7x36, 5x8x18,
      6x6x14, 6x6x15, 6x6x16, 6x6x18

...............................................................................

*2*
*
*


6x8x8 minimal by Helmut Postl
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|u |        |  |      u |  |ud|u       |u |  |  |ud|  | d|ud|  |u |ud   |u | d|
+  +--+--+  +  +--+  +--+  +--+--+--+--+--+  +  +--+  +--+  +  +  +--+--+--+--+
|     |  |u |u |u |  |  |  |      u | d| d| d|  |u |  |u |  |ud|  |  |u |   ud|
+  +--+  +  +  +--+--+  +  +--+--+--+--+--+  +  +  +  +--+--+--+  +  +--+--+--+
|  |u |  |  |        |  |  |    d   |        |u |  |  |  |u |  |  |     |ud   |
+--+--+  +--+--+--+--+  +  +--+--+  +--+--+--+--+  +  +  +--+  +--+  +--+--+--+
|   u    |u |u |   u    |  |u | d|  |ud|ud|  | d|  |  |ud|       d| d|      u |
+--+--+--+--+--+--+--+--+  +--+--+  +--+--+  +--+--+  +--+--+--+--+--+--+--+--+
|   u    |u |u |   u    |  |  | d|  |ud|ud|  | d|u |  |u       | d| d      |ud|
+  +--+--+--+--+  +--+--+  +  +--+--+--+--+  +--+--+  +--+--+--+  +--+  +--+  +
|  |        |  |  |u |  |  |  |u |        |    d   |  |   ud|     |  |  |u |  |
+  +--+--+  +  +  +--+  +  +  +  +  +--+--+--+--+--+  +--+--+--+  +  +--+--+--+
|  |  |u |u |u |  |     |  |u |  | d| d| d|u       |  |ud   |u |  |  |ud|  |u |
+--+  +--+  +  +--+--+  +  +--+  +  +--+--+--+--+--+  +--+--+--+--+  +  +  +--+
|u       |  |        |u |  |ud|  |  |u |      u |ud|  | d|u |   ud|u |  |ud| d|
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 1                     level 2                    level 3

+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|u | d|   ud| d|  |ud|u |  |ud|  |  | d|       d|ud|  | d      |  |        | d|
+--+--+--+--+  +  +  +--+  +--+  +  +--+--+--+--+--+  +--+  +--+  +  +--+--+  +
|ud   | d|  |  |ud|  | d|  | d|  |u |u |u | d      |  |  |  | d| d| d|  |     |
+--+--+--+  +  +--+--+--+  +  +  +  +--+--+--+--+--+  +  +--+--+  +  +  +--+  +
|   ud|     |  |  | d|  |  |  | d|        |   u    |  |  |        |  |  | d|  |
+--+--+--+  +--+  +--+  +  +  +--+--+--+--+  +--+--+  +  +--+--+--+--+  +--+--+
| d      |u |u       |ud|  |  |u |  |ud|ud|  |u | d|  |    d   | d| d|    d   |
+--+--+--+--+--+--+--+--+  +--+--+  +--+--+  +--+--+  +--+--+--+--+--+--+--+--+
|ud|      u |u |       d|  | d|u |  |ud|ud|  |u |  |  |    d   | d| d|    d   |
+  +--+  +--+  +--+--+--+  +--+--+  +--+--+--+--+  +  +--+--+  +--+--+--+--+  +
|  | d|  |  |     |ud   |  |   u    |        | d|  |  |  | d|  |  |        |  |
+--+--+--+  +  +--+--+--+  +--+--+--+--+--+  +  +  +  +  +--+  +  +  +--+--+  +
| d|  |ud|  |  | d|   ud|  |       d|u |u |u |  | d|  |     |  | d| d| d|  |  |
+--+  +  +  +--+--+--+--+  +--+--+--+--+--+  +  +--+  +  +--+--+  +  +--+  +--+
|u |ud|  | d|ud   | d|u |  |ud| d      | d|  |  |ud|  | d|        |  |       d|
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 4                     level 5                    level 6


same hexacube, allowing reflections

4x4x6 minimal
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|u |        |  |ud|      u |  | d      |ud|  |        | d|
+--+--+--+  +  +  +--+--+--+  +--+--+--+  +  +  +--+--+--+
|      u |u |  |  |u |ud| d|  |u |ud| d|  |  | d| d      |
+--+  +--+  +  +--+--+--+--+  +--+--+--+--+  +  +--+  +--+
|u |  |  |  |  |ud|      u |  | d      |ud|  |  |  |  | d|
+--+--+  +--+  +  +--+--+--+  +--+--+--+  +  +--+  +--+--+
|  |u       |  |  |ud|u |  |  |  | d|ud|  |  |       d|  |
+  +--+--+--+  +--+--+--+  +  +  +--+--+--+  +--+--+--+  +
|     |  |u |  |u       |ud|  |ud|       d|  | d|  |     |
+  +--+  +--+  +--+--+--+--+  +--+--+--+--+  +--+  +--+  +
|u |u       |  |ud|ud|u |u |  | d| d|ud|ud|  |       d| d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4

...............................................................................

2*
 2*


2x11x12 minimal
+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+
|  |u    |u    |u    |u    |u |u |  |    d|    d|    d|    d|    d| d|
+  +--+  +  +--+--+  +  +--+--+  +  +--+  +  +--+--+  +  +--+  +--+--+
|u    |  |  |u    |  |  |u |u    |  | d|  |  |    d|  |  |    d| d|  |
+--+--+--+--+  +--+--+--+--+  +--+  +  +--+--+  +--+--+--+--+--+--+  +
|     |u    |  |u    |u |u |  |u |  |     | d|  |    d|    d| d|    d|
+  +--+--+  +--+  +--+--+  +--+  +  +--+--+--+--+  +--+  +--+--+--+--+
|u |   u |u    |  |u |u    |     |  | d   | d| d|  |    d| d|  |     |
+--+--+  +--+--+--+--+  +--+--+--+  +  +--+--+--+--+--+--+--+  +--+  +
|     |   u |u |  |  |  |u |   u |  |  |     | d| d   |  |  | d   | d|
+  +--+--+--+--+  +  +--+--+--+  +  +--+--+  +--+  +--+  +  +--+  +--+
|u |   u |u |   u |   u |  |u |  |  | d   | d| d   | d   | d   | d|  |
+--+--+  +--+--+--+--+--+  +--+--+  +  +--+--+--+--+--+--+--+--+--+  +
|  |u |  |u    |u    |u |u    |u |  |  | d|    d|    d|    d| d|    d|
+  +--+--+--+  +  +--+--+--+--+  +  +--+  +--+  +  +--+  +--+  +--+--+
|u    |u |  |  |  |u |u    |     |  | d|    d|  |  |    d| d|     |  |
+--+--+--+  +--+--+--+--+  +--+--+  +  +--+  +--+--+--+--+--+--+--+  +
|     |   u |u |  |   u |u    |u |  |     |  | d| d   |  | d| d|    d|
+  +--+  +--+--+  +--+  +--+--+  +  +--+--+--+--+  +--+  +--+--+--+--+
|u |  |u |u |   u |  |   u |     |  | d   | d| d   | d   |  | d|     |
+--+  +--+--+--+--+  +--+--+--+--+  +  +--+--+--+--+--+--+  +--+--+  +
|   u |u |  |  |   u |  |  |   u |  |  | d| d   |  |  | d   |  |  | d|
+  +--+--+  +  +--+--+  +  +--+  +  +--+--+  +--+  +  +--+--+  +  +--+
|u |u |   u |   u |   u |   u |  |  | d| d   | d   | d   | d   | d   |
+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+
level 1                              level 2

also: 2x12x12 by George Sicherman
also: 4x10x42 by Helmut Postl


same hexacube, allowing reflections


2x8x9 co-minimal by George Sicherman
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|  |u    |u    |u    |u |  |    d|    d|    d|    d|
+  +--+  +  +--+  +--+--+  +--+  +  +--+  +--+  +--+
|u    |  |  |  |  |u |u |  | d|  |  |  |  |    d| d|
+--+--+--+--+  +--+--+  +  +  +--+--+  +--+--+--+--+
|     |  |u    |u |u    |  |     |    d|    d| d|  |
+  +--+  +--+--+--+  +--+  +--+--+--+--+  +--+--+  +
|u |   u |  |u |u |  |u |  | d   | d|    d| d|    d|
+--+--+--+  +--+  +--+  +  +  +--+  +--+--+--+--+--+
|     |   u |u    |     |  |  |     | d| d|     |  |
+  +--+  +--+  +--+--+--+  +--+--+--+--+--+  +--+  +
|u |  |u |u |  |u    |u |  | d   | d| d   | d|    d|
+--+  +--+--+--+  +--+  +  +  +--+--+  +--+--+--+--+
|   u |u |   u |  |     |  |  | d| d   | d   |     |
+  +--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+  +
|u |u |  |  |  |  |   u |  | d| d   |  |  |  |  | d|
+--+--+  +--+  +  +--+  +  +--+  +--+  +--+  +  +--+
|u |   u |   u |   u |  |  | d   | d   | d   | d   |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 1                     level 2


4x6x6 co-minimal
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |   u |  |   u |  | d u | d   |u | d|  |u | d|   u | d u |  | d   |  | d   | d|
+  +  +--+  +--+--+  +--+  +  +--+--+  +  +  +--+--+  +  +--+  +--+--+  +--+  +  +
|  |  |   u |     |  |u |  |  | d|   u |  | d   |u |  |  | d|  |     | d   |  |  |
+--+--+  +--+--+  +  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +  +--+--+  +--+--+
|   u |u |u    |u |  |  | d| d| d|    d|  |u    |u |u |u |  |  | d|    d| d| d   |
+--+  +--+--+  +--+  +  +--+--+--+--+  +  +  +--+--+--+--+  +  +--+  +--+--+  +--+
|u |   u |u |u    |  | d   | d| d| d|  |  |  |u |u |u |   u |  |    d| d| d   | d|
+  +--+--+  +--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+  +--+--+  +
|     |u    |  |  |  |u    | d|  |  |u |  | d|  |  |u |    d|  |  |  |    d|     |
+--+--+  +--+  +  +  +  +--+--+  +  +--+  +--+  +  +--+--+  +  +  +  +--+  +--+--+
|u    |  |u    |u |  | d|u |    d|u   d|  |u   d|u    | d|u |  | d|    d|  |    d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4

also: 2x7x12

...............................................................................

            ____
           /   /\
          /   /  \
         /   /   /
        /___/   /
       /\   \   \
  ____/  \   \   \
 /       /\   \  /
/_______/  \___\/
\       \  /
 \_______\/


allowing reflections


6x8x8 minimal by George Sicherman
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|     |   u |u |   u |  |  |   u |u | d| d u | d   |  |  | d| d u |u | d|     |
+--+  +--+--+  +--+--+  +  +  +--+--+  +--+--+--+  +  +  +--+--+--+  +--+  +--+
|u |   u |     |u |     |  | d|  | d|     | d   |u |  |     |u |     |u    | d|
+  +--+--+--+--+  +  +--+  +--+  +  +--+  +--+--+--+  +--+  +  +--+--+--+--+--+
|  |u    |u |     |u |  |  |u | d|  | d|  |    d|u |  | d|u |  |     |   u | d|
+--+--+  +--+  +--+--+  +  +  +--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+  +
|u    |     |  |u |  |u |  | d|     |u |u   d|    d|  |u    |    d| d|  |  |u |
+--+  +--+--+--+--+  +--+  +--+  +--+--+--+--+  +--+  +--+  +  +--+--+  +  +--+
|u |  |u |  |     |   u |  | d   | d u |u |     | d|  |u |  |  | d| d   |   u |
+  +--+--+  +--+  +--+--+  +--+--+--+--+  +--+--+  +  +  +--+--+  +--+--+--+--+
|  |u |     |u |   u |  |  |u | d   |  | d|  | d|u |  | d|u    |     |  |u | d|
+--+  +  +--+--+--+--+  +  +--+--+--+  +--+  +  +--+  +--+--+--+--+--+  +  +--+
|     |u |     |u    |u |  |u |    d|     | d|  | d|  | d|   u |     |u |     |
+  +--+--+  +--+--+  +--+  +  +--+--+--+  +--+--+  +  +--+  +--+  +--+--+--+  +
|  |u    |u |u    |     |  |    d|u   d| d|u |u    |  |     | d|u |u   d| d|  |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 1                     level 2                    level 3

+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|     |u | d| d u |u |  |  |   u | d u |u | d| d   |  |  | d   | d| d   |     |
+--+  +--+  +--+--+--+  +  +  +--+--+--+  +--+--+  +  +  +--+--+  +--+--+  +--+
|u |    d|     | d|     |  | d|   u |     |u |  |u |  |     | d|     | d   | d|
+--+--+--+--+--+  +  +--+  +--+--+--+  +--+  +  +--+  +--+  +  +--+--+--+--+  +
|u | d   |     |  | d|u |  | d|u    |  |u |  |u | d|  |  | d|     | d|    d|  |
+  +--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+  +  +  +--+--+  +--+  +--+--+
| d|  |  |u |u    |    d|  |u    |u   d| d|     |u |  | d|  | d|  |     |    d|
+--+  +  +--+--+  +  +--+  +--+  +--+--+--+--+  +--+  +--+  +--+--+--+--+  +--+
| d   |   u |u |  |  | d|  |u |     | d| d u |   u |  | d   |     |  | d|  | d|
+--+--+--+--+  +--+--+  +  +  +--+--+  +--+--+--+--+  +--+--+  +--+  +--+--+  +
|u | d|  |     |    d|u |  | d|u |  |u |  |   u | d|  |  | d   | d|     | d|  |
+--+  +  +--+--+--+--+--+  +--+  +  +--+  +--+--+--+  +  +--+--+--+--+  +  +--+
|     | d|     | d   |u |  |u |  |u |     |u    | d|  | d|    d|     | d|     |
+  +--+--+--+  +--+  +--+  +  +--+--+  +--+--+--+  +  +--+  +--+--+  +--+--+  +
|  |u |u   d| d|u |     |  |    d| d|u |u   d|u    |  |     |    d| d|    d|  |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 4                     level 5                    level 6

...............................................................................

**2*
 *

allowing reflections


4x12x12 by George Sicherman
+--+--+--+--+--+--+--+--+--+--+--+--+
|u |   u       |u |  |      u    |u |
+--+--+--+  +--+--+  +--+  +--+--+--+
|  |u |  |  |   u       |  |  |u |  |
+  +--+  +--+--+--+--+--+--+  +--+  +
|u |     |      u    |  |u |u |     |
+  +--+  +--+  +--+--+  +--+  +--+  +
|     |u |u |  |  |     |     |  |u |
+  +--+  +--+--+  +--+  +--+  +  +  +
|  |u |  |  |     |u |u |  |  |u |  |
+--+--+--+  +--+  +--+  +  +--+  +--+
|u |  |     |u |u |  |  |u |u |     |
+--+  +--+  +--+  +  +--+  +--+  +--+
|     |u |u |  |  |u |u |     |  |u |
+--+  +--+  +  +--+  +--+  +--+--+--+
|  |u |  |  |u |u |     |  |  |u |  |
+  +  +  +--+  +--+  +--+--+  +--+  +
|u |  |     |     |  |  |u |u |     |
+  +--+  +--+  +--+--+  +--+  +--+  +
|     |u |u |  |   u       |     |u |
+  +--+  +--+--+--+--+--+--+  +--+  +
|  |u |  |  |      u    |  |  |u |  |
+--+--+--+  +--+  +--+--+  +--+--+--+
|u |   u       |  |u |      u    |u |
+--+--+--+--+--+--+--+--+--+--+--+--+
level 1

+--+--+--+--+--+--+--+--+--+--+--+--+
|ud   | d|       d   |  |  | d|  |ud|
+--+--+--+--+  +--+--+  +  +--+  +  +
|    d      |  | d|     |     | d|  |
+--+--+  +--+--+--+--+  +  +--+  +--+
| d|  |  |  |u | d|  |u | d| d|     |
+--+  +--+  +--+--+  +  +  +--+  +--+
|     | d| d|  |     |  |  |  |  | d|
+--+  +--+  +  +--+  +--+--+  +--+--+
|  | d|     |     | d| d|     | d|  |
+  +  +--+  +  +--+  +--+--+  +--+  +
| d|  |  |  | d| d|  |  | d| d|     |
+  +--+  +--+  +--+--+  +--+  +--+  +
|     | d| d|  |  | d| d|  |  |  | d|
+  +--+  +--+--+  +--+  +  +--+  +  +
|  | d|     | d| d|     |     | d|  |
+--+--+  +--+--+  +--+  +  +--+  +--+
| d|  |  |  |  |     |  | d| d|     |
+--+  +--+  +  +  +--+--+  +--+  +--+
|     | d| d|u |  | d|u |  |  |  | d|
+--+  +--+  +  +--+--+--+--+  +--+--+
|  | d|     |     | d|  |       d   |
+  +  +--+  +  +--+--+  +--+--+--+--+
|ud|  | d|  |  |    d      | d|   ud|
+--+--+--+--+--+--+--+--+--+--+--+--+
level 2

+--+--+--+--+--+--+--+--+--+--+--+--+
|ud|  |u |  |  |   u       |u |   ud|
+  +  +--+  +  +--+--+  +--+--+--+--+
|  |u |     |     |u |  |      u    |
+--+  +--+  +  +--+--+--+--+  +--+--+
|     |u |u | d|  |u | d|  |  |  |u |
+--+  +--+  +  +  +--+--+  +--+  +--+
|u |  |  |  |  |     |  |u |u |     |
+--+--+  +--+--+  +--+  +  +--+  +--+
|  |u |     |u |u |     |     |u |  |
+  +--+  +--+--+  +--+  +  +--+  +  +
|     |u |u |  |  |u |u |  |  |  |u |
+  +--+  +--+  +--+--+  +--+  +--+  +
|u |  |  |  |u |u |  |  |u |u |     |
+  +  +--+  +  +--+  +--+--+  +--+  +
|  |u |     |     |u |u |     |u |  |
+--+  +--+  +  +--+  +--+--+  +--+--+
|     |u |u |  |     |  |  |  |  |u |
+--+  +--+  +--+--+  +  +  +--+  +--+
|u |  |  |  | d|u |  | d|u |u |     |
+--+--+  +--+--+--+--+  +  +--+  +--+
|   u       |  |u |     |     |u |  |
+--+--+--+--+  +--+--+  +  +--+  +  +
|ud   |u |      u    |  |  |u |  |ud|
+--+--+--+--+--+--+--+--+--+--+--+--+
level 3

+--+--+--+--+--+--+--+--+--+--+--+--+
| d|    d      |  | d|       d   | d|
+--+--+--+  +--+  +--+--+  +--+--+--+
|  | d|  |  |       d   |  |  | d|  |
+  +--+  +--+--+--+--+--+--+  +--+  +
|     | d| d|  |    d      |     | d|
+  +--+  +--+  +--+--+  +--+  +--+  +
| d|  |     |     |  |  | d| d|     |
+  +  +  +--+  +--+  +--+--+  +--+  +
|  | d|  |  | d| d|     |  |  | d|  |
+--+  +--+  +  +--+  +--+  +--+--+--+
|     | d| d|  |  | d| d|     |  | d|
+--+  +--+  +--+  +  +--+  +--+  +--+
| d|  |     | d| d|  |  | d| d|     |
+--+--+--+  +--+  +--+  +  +--+  +--+
|  | d|  |  |     | d| d|  |  | d|  |
+  +--+  +--+--+  +--+  +--+  +  +  +
|     | d| d|  |  |     |     |  | d|
+  +--+  +--+  +--+--+  +--+  +--+  +
| d|     |       d   |  | d| d|     |
+  +--+  +--+--+--+--+--+--+  +--+  +
|  | d|  |  |    d      |  |  | d|  |
+--+--+--+  +--+--+  +--+  +--+--+--+
| d|    d      | d|  |       d   | d|
+--+--+--+--+--+--+--+--+--+--+--+--+
level 4

...............................................................................

*2*
 *
 *


10x10x36 by Helmut Postl

...............................................................................

2
***
 *


10x10x48 by Helmut Postl


same hexacube, with reflections allowed

4x6x6 minimal, by George Sicherman
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |  |u    |  |u |  | d|   ud|u |    d|  |u    | d|ud   |u |  | d|  |    d|  | d|
+--+  +--+  +  +--+  +  +--+--+--+  +--+  +--+  +--+--+--+  +  +--+  +  +--+  +--+
|        |  |     |  |        |     |  |  |  |     |        |  |     |  |        |
+--+--+  +--+  +--+  +--+  +--+--+  +  +  +  +  +--+--+  +--+  +--+  +--+  +--+--+
|     |u |u    |u |  |u |  | d| d|  |ud|  |ud|  |u |u |  | d|  | d|    d| d|     |
+  +--+--+--+--+  +  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +  +--+--+--+--+  +
|u |   u |u |     |  |ud|  | d| d|  |u |  | d|  |u |u |  |ud|  |     | d| d   | d|
+--+  +--+  +--+--+  +  +  +--+--+  +--+  +--+  +--+--+  +  +  +--+--+  +--+  +--+
|     |  |        |  |  |     |        |  |        |     |  |  |        |  |     |
+--+  +  +--+  +--+  +--+  +--+--+--+  +  +  +--+--+--+  +--+  +--+  +--+  +  +--+
|u |  |   u |  |u |  | d   |u |ud   | d|  |u |   ud| d|   u |  | d|  | d   |  | d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4

...............................................................................

2*
 *
 **


10x10x72 by Helmut Postl

...............................................................................

*2
 *
 **


10x10x72 by Helmut Postl

...............................................................................

**2
*
*


10x10x72 by Helmut Postl


same hexacube, allowing reflections


4x4x6 minimal
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|      u |u |  |u |u | d|ud|  |ud|ud|    d|  | d| d      |
+  +--+--+  +  +  +  +--+--+  +--+--+--+--+  +--+--+--+--+
|  |     |  |  |  |  |u |u |  |       d|ud|  |  |       d|
+  +  +--+  +  +  +--+--+  +  +  +--+--+--+  +  +--+--+--+
|  |  |u |  |  |     |ud|  |  |  |u | d|  |  |  | d      |
+--+  +  +--+  +--+--+--+--+  +  +--+--+  +  +  +--+--+  +
|  |u |  |  |  |  |ud|     |  |  | d|u |  |  |       d|  |
+  +--+  +  +  +  +--+--+  +  +--+--+--+  +  +--+--+--+  +
|  |     |  |  |u |u |  |  |  |ud| d      |  | d      |  |
+  +--+--+  +  +--+--+  +  +  +--+--+--+--+  +--+--+--+--+
|u |u       |  |ud| d|u |u |  | d   |ud|ud|  |       d| d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4


4x6x6
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|     |  |u       |  |        |ud|u |  |  |        | d|ud|  |  |     |       d|  |
+  +--+  +--+--+  +  +--+--+  +--+--+  +  +--+--+  +--+--+  +  +--+  +  +--+--+  +
|  |u |      u |  |  |u |ud|  |u |ud|  |  |ud| d|  |ud| d|  |  | d|  |  | d      |
+  +  +--+--+--+--+  +--+--+  +--+--+  +  +--+--+  +--+--+  +  +  +  +--+--+--+--+
|u |  |u |u |     |  |ud|u | d| d      |  | d|ud|u |u       |  |  | d| d| d|     |
+--+  +--+--+  +--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +  +--+--+--+--+  +
|     |u |u |  |u |  |       d| d|u |ud|  |      u |u |ud| d|  |     | d| d| d|  |
+--+--+--+--+  +  +  +  +--+--+  +--+--+  +  +--+--+  +--+--+  +--+--+--+--+  +  +
|  |u       |u |  |  |  |ud|u |  |ud|u |  |  | d|ud|  | d|ud|  |       d|  |  | d|
+  +--+--+  +--+  +  +  +--+--+  +--+--+  +  +--+--+  +--+--+  +  +--+--+  +  +--+
|      u |  |     |  |  |u |ud|        |  |  |ud| d|        |  |  | d      |     |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4

...............................................................................

2**
 *
 *


10x10x72 by Helmut Postl


same hexacube, with reflections allowed

4x4x6 minimal, by George Sicherman
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|   u    |u |  |  |ud|u | d|  |u | d|ud|  |  | d|    d   |
+  +--+--+  +  +  +--+--+--+  +--+--+--+  +  +  +--+--+  +
|  |        |  |        |  |  |  |        |  |        |  |
+--+--+--+  +  +  +--+--+  +  +  +--+--+  +  +  +--+--+--+
|u |     |  |  | d|        |  |        |u |  |  |     | d|
+--+  +--+--+  +--+--+--+  +  +  +--+--+--+  +--+--+  +--+
|  |u |     |  |u |ud|u |u |  | d| d|ud| d|  |     | d|  |
+  +  +  +--+  +--+--+--+--+  +--+--+--+--+  +--+  +  +  +
|u |  |u |  |  |ud|u |ud|u |  | d|ud| d|ud|  |  | d|  | d|
+  +--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+  +
|     |  |u |  |u |      ud|  |ud      | d|  | d|  |     |
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4


also: 3x7x8 by George Sicherman
also: 3x4x10, 3x7x20, 3x8x8, 3x8x11, 3x8x12, 3x8x13, 3x9x16,
      4x5x30, 4x5x33, 4x5x36, 4x5x39, 4x5x42, 4x5x45, 4x5x48, 4x5x51,
      4x5x54, 4x5x57, 4x6x6, 4x6x9, 4x6x11, 5x6x8, 5x6x12, 6x6x6

...............................................................................

            ____
           /   /\
          /   /  \
         /   /   /
    ____/___/   /
   /    \   \   \
  /   ___\   \   \
 /   /\       \  /
/___/  \_______\/
\   \  /
 \___\/


12x12x72 by Helmut Postl

...............................................................................

*
***
 2

with reflections allowed


6x8x10
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|  |u    |  |u    |u |  |  |   ud|u |   ud|    d u |  |  | d|ud   | d|u    | d|
+  +--+--+  +--+--+  +  +  +  +--+--+  +--+--+--+--+  +  +--+--+  +--+--+--+--+
|        |   u |  |  |u |  |  |u    |  | d|u    |ud|  |   ud|u |  |   ud|u | d|
+--+  +--+  +--+  +--+--+  +--+--+--+--+--+--+--+  +  +--+--+--+--+  +--+--+--+
|  |u |     |u |        |  |u | d|  |u   d   |     |  | d u    | d|  |  |u |  |
+  +--+--+--+  +--+  +--+  +--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +  +  +
|u |u |u    |  |u |u |u |  |ud| d| d|     | d| d|ud|  | d|     |        |  | d|
+--+  +--+--+--+  +--+--+  +  +--+  +--+  +--+--+  +  +--+  +--+--+  +--+--+--+
|        |  |        |  |  |     |u |  |   u |     |  |u    | d|u |u | d|  |u |
+  +--+--+  +  +--+--+  +  +--+--+--+  +  +--+--+--+  +--+  +--+--+--+--+  +--+
|  |        |  |        |  |     |u    |  |u |     |  |u |  | d|u |u | d|   u |
+--+--+  +--+--+--+  +--+  +  +--+--+  +--+  +--+  +  +--+--+--+  +--+--+  +--+
|u |u |u |  |   u |u |u |  |ud| d| d|     | d| d|ud|  | d|  |        |     | d|
+--+  +--+  +--+--+--+  +  +--+--+--+--+--+  +--+--+  +  +  +  +--+--+--+--+--+
|        |u |     |u |  |  |     |    d u |  | d|u |  |  |u |  |  | d|   u   d|
+--+--+  +--+  +--+  +--+  +  +--+--+--+--+--+--+--+  +--+--+--+  +--+--+--+--+
|u |  |  |u    |        |  |ud|   u | d|  |   u |  |  | d|u |ud   |  |u |ud   |
+  +  +--+--+  +--+--+  +  +--+--+--+--+  +--+--+  +  +--+--+--+--+  +--+--+  +
|  |u |   u |  |   u |  |  |u   d   |ud   |u |ud   |  | d|   u | d|   ud| d|  |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 1                     level 2                    level 3

+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|u |    d|u |   ud|u |  |  | d u    |ud   | d|ud   |  |  | d|    d|  |    d|  |
+--+--+--+--+  +--+--+  +  +--+--+--+--+  +--+--+  +  +  +  +--+--+  +--+--+  +
|u | d|ud   |  | d|ud   |  |ud|    d|u |  |    d|  |  | d|  |  | d   |        |
+--+--+--+  +--+--+--+--+  +  +--+--+--+--+--+--+--+  +--+--+  +--+  +--+  +--+
|  | d|  |  |u |    d u |  |     |   u   d|  |u | d|  |        | d|     | d|  |
+  +  +  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+  +--+  +--+  +--+--+--+  +
|u |  |        |     |u |  |ud|u |u |     |u |u |ud|  | d| d| d|  |    d| d| d|
+--+--+--+  +--+--+  +--+  +  +--+--+  +--+  +--+  +  +--+--+  +--+--+--+  +--+
| d|  |u | d| d|u |    d|  |     | d   |  | d|     |  |  |        |  |        |
+--+  +--+--+--+--+  +--+  +--+--+--+  +  +--+--+--+  +  +--+--+  +  +--+--+  +
| d   |u | d| d|u |  | d|  |     | d|  |    d|     |  |        |  |        |  |
+--+  +--+--+  +--+--+--+  +  +--+  +--+  +--+--+  +  +--+  +--+--+--+  +--+--+
|u |     |        |  |u |  |ud|u |u |     |u |u |ud|  | d| d| d   |  | d| d| d|
+--+--+--+--+--+  +  +  +  +--+--+  +--+--+--+--+--+  +  +--+--+--+  +--+  +--+
|u   d   |u |  |  | d|  |  | d|u |  | d u    |     |  |  | d|     | d|        |
+--+--+--+--+  +--+--+--+  +--+--+--+--+--+--+--+  +  +--+  +--+  +--+  +--+--+
|   ud| d|  |   ud| d|u |  |  | d   |  |u | d   |ud|  |        |    d|  |  | d|
+  +--+--+  +--+--+--+--+  +  +--+--+  +--+--+--+--+  +  +--+--+  +--+--+  +  +
|  |u |ud   |u | d   |u |  |   ud| d|   ud|   u   d|  |  | d   |  | d   | d|  |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 4                     level 5                    level 6

also: 5x8x15
also: 5x8x18 by George Sicherman


...............................................................................
Heptacubes
...............................................................................


*
******


1x2x7 minimal
+--+--+--+--+--+--+--+
|  |                 |
+  +--+--+--+--+--+  +
|                 |  |
+--+--+--+--+--+--+--+

also: 1x9x21, 3x7x7

...............................................................................

**
*****


1x2x7 minimal
+--+--+--+--+--+--+--+
|     |              |
+     +--+--+--+     +
|              |     |
+--+--+--+--+--+--+--+

also: 1x11x49, 1x13x35, 1x19x21, 3x5x7

...............................................................................

***
****


1x2x7 minimal
+--+--+--+--+--+--+--+
|        |           |
+        +--+        +
|           |        |
+--+--+--+--+--+--+--+

also: 1x9x63, 1x11x21, 3x5x7

...............................................................................

***
***
*


+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u  u  u |  |u  u |  | d  d ud|  |ud ud|  |  |  | d|    d  d|
+--+--+--+  +--+--+  +--+--+--+  +--+--+  +  +  +--+--+--+--+
|u |        |        |ud|        |        | d|        |
+  +        +        +  +        +        +  +        +
|u |        |        |ud|        |        | d|        |
+--+--+--+--+        +--+--+--+--+        +--+--+--+--+
level 1               level 2              level 3


3x3x7 minimal
+--+--+--+--+--+--+--+
|                 |  |
+           +--+--+  +
|           |        |
+           +        +
|           |        |
+--+--+--+--+--+--+--+
(3 levels deep)


also: 1x14x14 by David Klarner
also: 1x11x35, 1x11x42, 1x11x49, 1x11x56, 1x11x63, 1x12x21, 1x12x28, 1x12x35,
       1x14x19, 1x14x20, 1x14x22, 1x14x23, 1x14x24, 1x14x25, 1x14x26, 1x14x27,
       1x14x29, 1x14x30, 1x14x31, 1x14x32, 1x14x35, 1x15x21, 1x15x28, 1x15x35,
       1x16x21, 1x16x28, 1x16x35, 1x17x21, 1x17x28, 1x17x35, 1x18x21, 1x18x28,
       1x18x35, 1x19x21, 1x20x21, 1x21x21, 1x21x22, 1x21x23, 1x21x25, 1x21x26
also: 3x4x7, 3x5x7, 4x4x7, 4x5x7, 5x5x7

...............................................................................

 **
*****


2x7x8 minimal
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|  |u  u |      u  u    |  |    d  d      | d  d|  |
+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +
|  |u  u |      u  u    |  |    d  d      | d  d|  |
+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +
|     |              |  |  |  |              |     |
+     +--+--+     +--+  +  +  +--+     +--+--+     +
|     |     |     |     |  |     |     |     |     |
+  +--+     +--+--+     +  +     +--+--+     +--+  +
|  |              |     |  |     |              |  |
+--+--+--+--+--+--+--+  +  +  +--+--+--+--+--+--+--+
|   u  u       |u  u |  |  |  | d  d|       d  d   |
+--+--+--+--+--+--+--+  +  +  +--+--+--+--+--+--+--+
|   u  u       |u  u |  |  |  | d  d|       d  d   |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 1                     level 2


   +--+              +--+
   |x |              |x |
   +--+--+--+        +  +--+--+
   |     |x |        |  |   x |
+--+     +--+--+  +--+--+--+--+--+
|              |  |  |  |  |  |  |
+--+--+--+--+--+  +  +  +  +  +  +
|x |x |x |x |x |  |x |x |x |x |x |
+--+--+--+--+--+  +--+--+--+--+--+
levels 1, 4, 5     levels 2, 3


+--+--+--+--+     +--+--+--+--+
|x |     |x |     |x    |   x |
+--+     +--+--+  +--+--+--+--+--+
|              |  |  |  |  |  |  |
+--+--+--+--+--+  +  +  +  +  +  +
|x |x |x |x |x |  |x |x |x |x |x |
+--+--+--+--+--+  +--+--+--+--+--+
levels 1, 4, 5     levels 2, 3


5x5x7
+--+--+--+--+--+--+--+
|  |              |  |
+  +--+--+     +--+  +
|     |  |     |     |
+     +  +--+--+     +
|     |        |     |
+  +--+        +--+  +
|  |              |  |
+  +              +  +
|  |              |  |
+--+--+--+--+--+--+--+
(5 levels deep)


3x5x14
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|           |              |              |
+           +--+     +--+--+              +
|              |     |     |              |
+              +--+--+     +--+           +
|              |              |           |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
(5 levels deep)

also: 1x19x28 (by T.W. Marlow and Karl A. Dahlke, independently), many others

...............................................................................

*   *
*****


   +--+--+--+        +--+--+--+
   |u |u |u |        | d| d| d|
+--+--+--+--+--+  +--+  +  +  +--+
|u           u |  | d|  |  |  | d|
+--+--+--+--+--+  +--+  +  +  +--+
|u           u |  | d|  |  |  | d|
+--+--+--+--+--+  +--+  +  +  +--+
|u           u |  | d|  |  |  | d|
+--+--+--+--+--+  +--+  +  +  +--+
   |u |u |u |        | d| d| d|
   +--+--+--+        +--+--+--+
level 1               level 2


2x5x7 minimal by Andrew Clarke
+--+--+--+--+--+--+--+
|     |        |     |
+  +--+        +--+  +
|  |              |  |
+  +              +  +
|  |              |  |
+  +              +  +
|  |              |  |
+  +--+        +--+  +
|     |        |     |
+--+--+--+--+--+--+--+
(2 levels deep)

...............................................................................

* **
****


+--+--+--+        +--+--+--+
|x    |  |        |x |     |
+--+--+  +        +--+  +--+
|x    |x |        |x |  |x |
+--+--+--+--+     +--+  +--+--+
|x    |   x |     |x |     |x |
+--+--+--+--+     +--+     +--+
|x    |   x |     |x |     |x |
+--+--+--+--+     +--+--+--+--+
levels 1, 2, 4     level 3


4x4x7 minimal
+--+--+--+--+--+--+--+
|        |           |
+        +           +
|        |           |
+        +--+        +
|           |        |
+           +        +
|           |        |
+--+--+--+--+--+--+--+
(4 levels deep)

also: 4x6x14

...............................................................................

 *
**
****


4x4x7 minimal
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|      u  u |  |  |u |ud  d|  |u  ud| d|  |  | d  d      |
+--+--+--+--+  +  +--+--+--+  +--+--+--+  +  +--+--+--+--+
|      u  u |  |  |u |ud  d|  |u  ud| d|  |  | d  d      |
+--+--+--+--+  +  +--+--+--+  +--+--+--+  +  +--+--+--+--+
|           |  |        |  |  |  |        |  |           |
+     +--+--+  +     +--+  +  +  +--+     +  +--+--+     +
|     |u |u |  |     | d| d|  |u |u |     |  | d| d|     |
+--+  +  +  +  +--+--+  +  +  +  +  +--+--+  +  +  +  +--+
|u |  |u |u |  |ud|u |ud|ud|  |ud|ud| d|ud|  | d| d|  | d|
+--+--+  +--+  +--+--+--+--+  +--+--+--+--+  +--+  +--+--+
|u  u |  |u |  |ud  d   |ud|  |ud|   u  ud|  | d|  | d  d|
+--+--+  +--+  +--+--+--+--+  +--+--+--+--+  +--+  +--+--+
|u  u |  |u |  |ud  d   |ud|  |ud|   u  ud|  | d|  | d  d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4

...............................................................................

*  *
*****


+--+--+--+--+--+  +--+--+--+--+--+
|x |x |x |x |x |  |x |x |x |x |x |
+--+--+--+--+--+  +  +  +  +  +  +
|              |  |  |  |  |  |  |
+  +--+--+  +--+  +--+--+--+--+--+
|  |x |x |  |     |   x |x    |
+--+--+--+--+     +--+--+--+--+
levels 1, 3, 4     levels 2, 5


            +--+              +--+
            |x |              |x |
+--+--+--+--+--+  +--+--+--+--+  +
|x |  |x |x |  |  |x |   x |x |  |
+--+  +--+--+  +  +  +--+--+  +--+
|              |  |  |  |  |  |  |
+--+--+--+--+--+  +--+  +  +--+  +
   |x |x |  |x |     |x |x |  |x |
   +--+--+  +--+     +--+--+  +--+
levels 1, 3, 4     levels 2, 5


5x5x7 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+--+
|     |     |        |
+  +--+     +        +
|  |        |        |
+  +        +        +
|  |        |        |
+  +--+     +        +
|     |     |        |
+  +--+     +--+     +
|  |           |     |
+--+--+--+--+--+--+--+
(5 levels deep)

also: 5x6x7, 5x8x14, 5x9x14

...............................................................................

* *
*****


      +--+--+              +--+--+
      |x |x |              |x |x |
+--+--+--+--+--+--+  +--+--+  +  +--+--+
|              |x |  |  |  |  |  |   x |
+--+--+  +--+  +--+  +  +  +--+--+--+--+
|x |x |  |x |  |x |  |x |x |   x |   x |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
levels 1, 2, 4        levels 3, 5


+--+--+--+--+     +--+--+--+--+
|  |x |  |x |     |   x |   x |
+  +--+  +--+--+  +--+--+--+--+--+
|              |  |  |  |  |  |  |
+--+--+--+--+--+  +  +  +  +  +  +
|x |x |x |x |x |  |x |x |x |x |x |
+--+--+--+--+--+  +--+--+--+--+--+
levels 1, 2, 4     levels 3, 5


3x5x14 co-minimal
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|           |              |              |
+           +--+--+  +--+  +              +
|              |  |  |  |  |              |
+              +  +--+  +--+--+           +
|              |              |           |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
(5 levels deep)


5x6x7 co-minimal
+--+--+--+--+--+--+
|        |        |
+        +        +
|        |        |
+        +        +
|        |        |
+        +        +
|        |        |
+     +--+--+     +
|     |     |     |
+--+--+     +--+--+
|                 |
+                 +
|                 |
+--+--+--+--+--+--+
(5 levels deep)

...............................................................................

 * *
*****


+--+--+--+--+     +--+--+--+--+
|x |  |x |  |     |x    |x    |
+--+  +--+  +--+  +--+--+--+--+--+
|              |  |  |  |  |  |  |
+--+--+--+--+--+  +  +  +  +  +  +
|x |x |x |x |x |  |x |x |x |x |x |
+--+--+--+--+--+  +--+--+--+--+--+
levels 1, 3, 5     levels 2, 4


3x5x14 co-minimal
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|           |              |              |
+           +--+  +--+  +--+              +
|              |  |  |  |  |              |
+              +--+  +--+  +--+           +
|              |              |           |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
(5 levels deep)


5x6x7 co-minimal
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |   u     u    |  |ud|  | d|  | d|  |  |ud|   u     u    |  |ud|  | d|  | d|  |  | d|              |
+--+--+--+--+--+--+  +  +  +--+  +--+  +  +--+--+--+--+--+--+  +  +  +--+  +--+  +  +--+--+  +--+  +--+
|  |u |  |u |  |u |  |  |ud|  |ud|  |ud|  |  |ud|  |ud|  |ud|  |  |ud|  |ud|  |ud|  |  | d|  | d|  | d|
+  +--+  +--+  +--+  +--+--+  +--+  +--+  +  +--+  +--+  +--+  +--+--+  +--+  +--+  +  +--+--+--+--+--+
|u |              |  | d|              |  |     |     |     |  |u |              |  | d|              |
+  +--+--+--+--+--+  +--+--+--+--+--+--+  +  +--+  +--+  +--+  +--+--+--+--+--+--+  +  +--+  +--+  +--+
|  |u |  |u |  |u |  |   ud|   ud|   ud|  |  |ud|  |ud|  |ud|  |   ud|   ud|   ud|  |  | d|  | d|  | d|
+  +--+  +--+  +--+  +--+--+--+--+--+--+  +  +--+  +--+  +--+  +--+--+--+--+--+--+  +  +--+--+--+--+--+
|u |              |  | d|              |  |     |     |     |  |u |              |  | d|              |
+  +--+--+--+--+--+  +--+--+  +--+  +--+  +  +--+  +--+  +--+  +--+--+  +--+  +--+  +  +--+  +--+  +--+
|  |u |  |u |  |u |  |  |ud|  |ud|  |ud|  |  |ud|  |ud|  |ud|  |  |ud|  |ud|  |ud|  |  | d|  | d|  | d|
+--+--+  +--+  +--+  +  +  +--+  +--+  +  +--+--+--+--+--+--+  +  +  +--+  +--+  +  +--+--+--+--+--+--+
|u |              |  |ud|  |u |  |u |  |  |ud|    d     d   |  |ud|  |u |  |u |  |  | d|    d     d   |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4              level 5

...............................................................................

*
*
*****


5x6x7 minimal
+--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |        |u |u |  | d      |  | d| d|
+--+  +--+--+--+--+  +--+--+--+  +  +  +
|  |  |u |        |  |       d|  |  |  |
+  +  +--+--+--+  +  +--+--+--+  +  +  +
|  |  |u |u |  |  |  |       d| d|  |  |
+  +  +--+--+  +  +  +--+--+--+--+--+--+
|  |  |u |u |  |  |  |       d| d      |
+  +  +--+--+  +  +  +--+--+--+--+--+--+
|  |  |u |u |  |  |  |  |  | d| d      |
+  +--+--+--+  +  +  +  +  +  +--+--+--+
|        |u |  |  |  |  |  |  | d      |
+--+--+--+--+  +--+  +  +  +  +--+--+--+
|u |u |        |u |  | d| d|  |       d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+
levels 1, 2, 3, 4     level 5

...............................................................................

 *
******


+--+--+                 +--+--+
|x |  |                 |x    |
+--+  +--+--+--+--+     +--+--+--+--+--+--+
|                 |     |  |  |  |  |  |  |
+--+--+--+--+--+--+     +  +  +  +  +  +  +
|x |x |x |x |x |x |     |x |x |x |x |x |x |
+--+--+--+--+--+--+     +--+--+--+--+--+--+
levels 1, 3, 4, 5, 6     level 2


3x6x14 by Andrew Clarke
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|     |                 |                 |
+     +--+--+--+--+  +--+                 +
|                 |  |  |                 |
+                 +--+  +--+--+--+--+     +
|                 |                 |     |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
(6 levels deep)

...............................................................................

  *
******


+--+--+--+--+--+--+     +--+--+--+--+--+--+
|  |x |  |x |  |x |     |   x |   x |   x |
+  +--+  +--+  +--+     +--+--+--+--+--+--+
|  |x |  |x |  |x |     |   x |   x |   x |
+  +--+  +--+  +--+     +--+--+--+--+--+--+
|  |x |  |x |  |        |   x |  |x    |
+  +--+  +--+  +--+     +--+--+  +--+--+--+
|     |     |     |     |                 |
+  +--+  +--+  +--+     +--+--+--+--+--+--+
|  |x |  |x |  |x |     |   x |   x |   x |
+  +--+  +--+  +--+     +--+--+--+--+--+--+
|  |x |  |x |  |x |     |   x |   x |   x |
+--+--+--+--+--+--+     +--+--+--+--+--+--+
levels 1, 2, 3, 5, 6     level 4


6x6x7 minimal
+--+--+--+--+--+--+--+
|                 |  |
+                 +  +
|                 |  |
+              +--+  +
|              |     |
+              +--+  +
|                 |  |
+                 +  +
|                 |  |
+                 +  +
|                 |  |
+--+--+--+--+--+--+--+
(6 levels deep)

also: 6x7x10, 6x8x14

...............................................................................

*
****
**


3x7x8 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|u |u |u |        |u |  |ud|ud|ud|      u  ud|  | d| d| d|     | d  d|
+  +  +  +--+     +--+  +  +  +  +--+--+--+--+  +--+--+--+     +--+--+
|u |u |u |  |     |u |  | d| d| d|      u  ud|  |  |           | d  d|
+--+--+--+  +  +--+--+  +  +  +  +--+--+--+--+  +  +--+--+--+  +--+--+
|        |  |  |u  u |  |  |  |  |       d ud|  |           |  |  | d|
+     +--+  +  +--+--+  +  +  +  +--+--+--+--+  +     +--+--+--+  +--+
|     |     |  |u  u |  |  |  |  |       d ud|  |     |        |  | d|
+--+  +     +--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+     +  +--+
|u |  |        |     |  |ud u       |  |  |  |  | d  d|  |     |     |
+--+  +--+--+--+     +  +--+--+--+--+  +  +  +  +--+--+  +  +--+     +
|u |  |  |           |  |ud u       |  |  |  |  | d  d|  |  |        |
+--+--+  +--+--+--+  +  +--+--+--+--+  +  +  +  +--+--+  +  +--+--+--+
|u  u |           |  |  |ud  d      |u |u |u |  | d|     |  | d| d| d|
+--+--+     +--+--+--+  +--+--+--+--+  +  +  +  +--+     +--+  +  +  +
|u  u |     |u |u |u |  |ud  d      |ud|ud|ud|  | d|        | d| d| d|
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2                 level 3


6x6x7
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|        |u |        |  |        |ud|        |  |u |u |u  ud|  |u |u |
+--+     +--+     +--+  +--+     +--+     +--+  +  +--+--+--+  +--+  +
|u |     |u |     |u |  |ud|     |ud|     |ud|  |ud|u |u  ud|  |u |ud|
+--+  +--+--+--+  +--+  +--+  +--+--+--+  +--+  +--+--+--+--+  +--+--+
|u |  |        |  |u |  |ud|  |        |  |ud|  | d|u  u    |     | d|
+  +  +--+     +  +  +  +  +  +--+     +  +  +  +--+--+--+--+     +--+
|u |  |u |     |  |u |  | d|  |ud|     |  | d|  |  |u  ud|        |  |
+--+--+--+  +--+--+--+  +  +--+--+  +--+--+  +  +  +--+--+--+--+--+  +
|   u  u |  |u  u    |  |  |ud  d|  | d ud|  |  |u |ud|u  u    |ud|u |
+--+--+--+  +--+--+--+  +  +--+--+  +--+--+  +  +  +--+--+--+--+--+  +
|   u  u |  |u  u    |  |  |ud  d|  | d ud|  |  |u |ud|u  u    |ud|u |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2                 level 3

+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
| d|ud| d  d   |ud| d|  |  |ud u |  |u  ud|  |  |    d  d|  | d  d   |
+  +--+--+--+--+--+  +  +  +--+--+  +--+--+  +  +--+--+--+  +--+--+--+
| d|ud| d  d   |ud| d|  |  |ud u |  |u  ud|  |  |    d  d|  | d  d   |
+  +--+--+--+--+--+  +  +  +--+--+  +--+--+  +  +--+--+--+  +--+--+--+
|  | d ud|        |  |  |u |  |ud|     |  |u |  | d|  | d|     |  | d|
+--+--+--+--+     +--+  +  +  +--+     +  +  +  +  +  +--+     +  +  +
|u | d  d   |     |u |  |ud|  |        |  |ud|  | d|  |        |  | d|
+--+--+--+--+  +--+--+  +--+  +--+--+--+  +--+  +--+  +--+--+--+  +--+
|ud| d| d ud|  | d|ud|  |ud|     |ud|     |ud|  | d|     | d|     | d|
+  +--+--+--+  +--+  +  +--+     +--+     +--+  +--+     +--+     +--+
| d| d| d ud|  | d| d|  |        |ud|        |  |        | d|        |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 4                  level 5                 level 6

...............................................................................

 *****
**


2x10x14 minimal
+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+
|            u |              |  |  |  |  |  | d   |  |  |  |  |
+--+--+--+--+--+  +--+--+--+--+  +  +  +  +  +--+--+  +  +  +  +
|u |u |u |u |     |u |u |u |u |  | d| d| d| d|     | d| d| d| d|
+  +  +  +  +--+--+  +  +  +  +  +--+--+--+--+  +--+--+--+--+--+
|  |  |  |  |   u |  |  |  |  |  |              | d            |
+  +  +  +  +--+--+  +  +  +  +  +--+--+--+--+--+--+--+--+--+--+
|  |  |  |  |   u |  |  |  |  |  |  |  |  |  |  | d            |
+  +  +  +  +--+--+  +  +  +  +  +  +  +  +  +  +--+--+--+--+--+
|  |  |  |  |   u |  |  |  |  |  |  |  |  |  |  | d            |
+  +  +  +  +--+--+  +  +  +  +  +  +  +  +  +  +--+--+--+--+--+
|  |  |  |  |     |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
+--+--+--+--+  +--+--+--+--+--+  +  +  +  +  +  +  +  +  +  +  +
|              |u |u |u |u |u |  |  |  |  |  |  | d| d| d| d| d|
+--+--+--+--+--+  +  +  +  +  +  +  +  +  +  +  +--+--+--+--+--+
|u |u |u |u |u |  |  |  |  |  |  | d| d| d| d| d|              |
+  +  +  +  +  +  +  +  +  +  +  +--+--+--+--+--+  +--+--+--+--+
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |     |  |  |  |  |
+--+--+--+--+--+  +  +  +  +  +  +  +  +  +  +--+--+  +  +  +  +
|            u |  |  |  |  |  |  |  |  |  |  | d   |  |  |  |  |
+--+--+--+--+--+  +  +  +  +  +  +  +  +  +  +--+--+  +  +  +  +
|            u |  |  |  |  |  |  |  |  |  |  | d   |  |  |  |  |
+--+--+--+--+--+--+--+--+--+--+  +  +  +  +  +--+--+  +  +  +  +
|            u |              |  |  |  |  |  | d   |  |  |  |  |
+--+--+--+--+--+  +--+--+--+--+  +  +  +  +  +--+--+  +  +  +  +
|u |u |u |u |     |u |u |u |u |  | d| d| d| d|     | d| d| d| d|
+  +  +  +  +--+--+  +  +  +  +  +--+--+--+--+  +--+--+--+--+--+
|  |  |  |  |   u |  |  |  |  |  |              | d            |
+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+
level 1                           level 2


+--+--+--+           +--+--+--+     +--+--+--+     +--+--+--+
|  |u |  |           |u   d|u |     | d|u   d|     |  | d|  |
+  +--+  +           +--+--+--+     +--+--+--+     +  +--+  +
|  |u |  |           |u   d|u |     | d|u   d|     |  | d|  |
+  +--+  +           +--+--+--+     +--+--+--+     +  +--+  +
|  |u |  |           |u   d|u |     | d|u   d|     |  | d|  |
+  +--+  +--+        +--+--+--+--+  +--+--+--+--+  +  +--+  +--+
|  |u |  |u |        |u   d|u   d|  | d|u | d|u |  |  | d|  | d|
+  +--+  +--+        +--+--+--+--+  +--+  +--+  +  +  +--+  +--+
|     |     |        |u |u |u |u |  | d| d| d| d|  |     |     |
+--+  +--+  +        +--+--+--+--+  +  +--+  +--+  +--+  +--+  +
|u |  |u |  |        | d u | d u |  |u | d|u | d|  | d|  | d|  |
+--+--+--+--+        +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
levels 1, 2, 3, 4     level 5        level 6        levels 7, 8, 9, 10


6x7x10
+--+--+--+--+--+--+--+
|        |           |
+        +           +
|        |           |
+        +           +
|        |           |
+        +--+        +
|           |        |
+           +        +
|           |        |
+           +        +
|           |        |
+--+--+--+--+--+--+--+
(10 levels deep)

...............................................................................

 *
2****


2x2x7 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|u |  |            u |  | d            |  | d|
+--+  +--+--+--+  +--+  +--+  +--+--+--+  +--+
|u             |  |u |  | d|  |             d|
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2

...............................................................................

2*
 ****


2x2x7 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|u    |           |u |  | d|           |    d|
+--+  +--+--+--+  +--+  +--+  +--+--+--+  +--+
|u |           |   u |  | d   |           | d|
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2

...............................................................................

**2*
**


2x2x7 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|      u    |u |     |  |     | d|    d      |
+     +--+--+--+     +  +     +--+--+--+     +
|     |u |   u       |  |       d   | d|     |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2

...............................................................................

 **
2***


2x2x7 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|u |     |         u |  | d         |     | d|
+--+     +--+     +--+  +--+     +--+     +--+
|u          |     |u |  | d|     |          d|
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2

...............................................................................

2**
 ***


2x2x7 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|u       |        |u |  | d|        |       d|
+--+     +--+     +--+  +--+     +--+     +--+
|u |        |      u |  | d      |        | d|
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2

...............................................................................

2*
 *2*


2x2x7 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|u    |u |   u    |u |  | d|    d   | d|    d|
+--+  +--+--+--+  +--+  +--+  +--+--+--+  +--+
|u |   u    |u |   u |  | d   | d|    d   | d|
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2

...............................................................................

             _________
            /        /\
  ____    _/________/  \
 /   /\  / \        \  /
/___/  \/   \    ____\/
\   \  /    /\   \  /
 \   \/____/  \___\/
  \        \  /
   \________\/


2x2x7 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|u |   u |   u |   u |  | d   | d   | d   | d|
+--+  +--+--+--+  +--+  +--+  +--+--+--+  +--+
|u    |u    |u    |u |  | d|    d|    d|    d|
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2

...............................................................................

2
*****


5x5x28 by Patrick Hamlyn
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
|     |     |u |  |             d|  |              |  |              |  |              |
+--+  +--+  +  +  +--+--+--+--+--+  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+
|  |u |u |u |  |  |u |ud|ud|ud|u |  | d|ud|ud|ud| d|  |u |ud|ud|ud|u |  | d| d| d| d| d|
+  +--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+  +  +--+--+--+--+--+  +--+--+  +--+--+
|u |     |     |  | d            |  |              |  |              |  |  |     |     |
+--+--+  +--+  +  +--+--+--+--+--+  +--+--+--+--+--+  +  +--+--+--+--+  +  +--+--+  +--+
|u |u |u |u |u |  | d|ud|ud|ud|ud|  |u |ud|ud|ud|ud|  | d|ud|ud|ud|ud|  |    d| d| d| d|
+  +--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
|              |  |              |  |              |  |u             |  | d|     |     |
+--+--+--+--+--+  +  +--+--+--+--+  +--+--+--+--+  +  +--+--+--+--+--+  +  +  +--+  +--+
|u |u |u |u |u |  | d|ud|ud|ud| d|  |u |ud|ud|ud|u |  | d|ud|ud|ud| d|  |  | d| d| d|  |
+--+--+  +--+--+  +--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+  +
|     |     |  |  |              |  |              |  |            u |  |     |     | d|
+--+  +--+--+  +  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +  +--+  +--+--+
|u |u |u |u    |  |ud|ud|ud|ud|u |  |ud|ud|ud|ud| d|  |ud|ud|ud|ud|u |  | d| d| d| d| d|
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+  +  +--+--+--+--+--+  +--+--+--+--+  +
|     |     |u |  |             d|  |              |  |              |  |              |
+--+  +--+  +  +  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+  +  +--+--+--+--+--+
|u |u |u |u |  |  |ud|ud|ud|ud|u |  |ud|ud|ud|ud| d|  |ud|ud|ud|ud|u |  | d| d| d| d| d|
+  +--+  +--+--+  +--+--+--+--+--+  +--+--+--+--+  +  +--+--+--+--+--+  +--+--+--+--+--+
|     |     |u |  |             d|  |              |  |              |  |              |
+--+--+--+--+  +  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+
|   u |u |u |  |  |u |ud|ud|ud|u |  | d|ud|ud|ud| d|  |u |ud|ud|ud|u |  | d| d| d| d| d|
+  +--+--+  +--+  +  +--+--+--+--+  +--+--+--+--+  +  +--+--+--+--+--+  +--+--+  +--+--+
|  |     |     |  |              |  |              |  |              |  |  |     |     |
+--+--+  +--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +  +--+--+--+--+  +  +--+--+  +--+
|u |u |u |u |u |  | d|ud|ud|ud|ud|  |u |ud|ud|ud|ud|  | d|ud|ud|ud|ud|  |    d| d| d| d|
+  +--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+  +
|              |  |              |  |              |  |u             |  | d|     |     |
+--+--+--+--+--+  +  +--+--+--+--+  +--+--+--+--+  +  +--+--+--+--+--+  +  +  +--+--+--+
|u |u |u |u |u |  | d|ud|ud|ud| d|  |u |ud|ud|ud|u |  | d|ud|ud|ud| d|  |  | d| d| d|  |
+--+--+  +--+--+  +--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+--+  +--+--+--+  +  +
|     |     |  |  |              |  |              |  |            u |  |     |     | d|
+--+  +--+--+  +  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +  +--+--+--+--+
|u |u |u |u    |  |ud|ud|ud|ud|u |  |ud|ud|ud|ud| d|  |ud|ud|ud|ud|u |  | d| d| d| d| d|
+--+--+  +--+--+  +--+--+--+--+--+  +--+--+--+--+  +  +--+--+--+--+--+  +--+--+--+--+  +
|     |     |  |  |              |  |              |  |              |  |              |
+--+  +--+--+  +  +--+--+--+--+  +  +--+--+--+--+--+  +--+--+--+--+  +  +--+--+--+--+--+
|u |u |u |u    |  |ud|ud|ud|ud|u |  |ud|ud|ud|ud| d|  |ud|ud|ud|ud|u |  | d| d| d| d| d|
+  +--+  +--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
|     |     |u |  |             d|  |              |  |              |  |              |
+--+--+--+--+  +  +--+--+--+--+--+  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+
|   u |u |u |  |  |u |ud|ud|ud|u |  | d|ud|ud|ud| d|  |u |ud|ud|ud|u |  | d| d| d| d| d|
+  +--+--+  +--+  +--+--+--+--+--+  +--+--+--+--+  +  +--+--+--+--+--+  +--+--+  +--+--+
|  |     |     |  |              |  |              |  |              |  |  |     |     |
+--+--+  +--+--+  +  +--+--+--+--+  +--+--+--+--+--+  +  +--+--+--+--+  +  +--+--+  +--+
|u |u |u |u |u |  | d|ud|ud|ud|ud|  |u |ud|ud|ud|ud|  | d|ud|ud|ud|ud|  |    d| d| d| d|
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+  +
|              |  |              |  |              |  |u             |  | d|     |     |
+--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +--+--+--+--+--+  +  +  +--+--+--+
|u |u |u |u |u |  | d|ud|ud|ud| d|  |u |ud|ud|ud|u |  | d|ud|ud|ud| d|  |  | d| d| d   |
+--+--+  +--+--+  +--+--+--+--+--+  +  +--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+  +
|     |     |  |  |              |  |              |  |              |  |     |     |  |
+--+  +--+--+  +  +--+--+--+--+  +  +--+--+--+--+--+  +--+--+--+--+  +  +  +--+  +--+--+
|u |u |u |u    |  |ud|ud|ud|ud|u |  |ud|ud|ud|ud| d|  |ud|ud|ud|ud|u |  | d| d| d| d| d|
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
level 1            level 2           level 3           level 4           level 5


same heptacube, allowing reflections


2x3x7 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|u |u             |u |  | d| d|             d|
+  +--+--+--+--+--+  +  +--+  +--+--+--+--+--+
|              |  |  |  |  |  |              |
+--+--+--+--+--+  +--+  +  +--+--+--+--+--+  +
|u             |u |u |  | d|             d| d|
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2

...............................................................................

22
***


4x4x7 minimal
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|u  u    |u |  | d  d|    d|  |u    |u  u |  | d|    d  d|
+--+--+--+  +  +     +     +  +     +     +  +  +--+--+--+
|        |u |  |     |    d|  |u    |     |  | d|        |
+--+     +  +  +--+--+--+--+  +--+--+--+--+  +  +     +--+
|u |u  u |  |  |ud| d  d|u |  | d|u  u |ud|  |  | d  d| d|
+  +--+--+--+  +  +--+--+--+  +--+--+--+  +  +--+--+--+  +
|u  u |u  u |  | d  d| d  d|  |u  u |u  u |  | d  d| d  d|
+--+--+--+  +  +--+--+--+  +  +  +--+--+--+  +  +--+--+--+
|  |u  u |u |  |u | d  d|ud|  |ud|u  u | d|  | d| d  d|  |
+  +     +--+  +--+--+--+--+  +--+--+--+--+  +--+     +  +
|u |        |  | d   |     |  |     |   u |  |        | d|
+  +--+--+--+  +     +     +  +     +     +  +--+--+--+  +
|u |   u  u |  | d   | d  d|  |u  u |   u |  | d  d   | d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4


same heptacube, allowing reflections


2x3x7 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|u  u |u  u    |u  u |  | d  d| d  d|    d  d|
+     +--+--+--+     +  +--+--+     +--+--+--+
|        |     |     |  |     |     |        |
+--+--+--+     +--+--+  +     +--+--+--+     +
|u  u    |u  u |u  u |  | d  d|    d  d| d  d|
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2

also: 4x4x7

...............................................................................

2**
2 *


+--+--+        +--+--+
|u  u |        | d  d|
+  +--+--+--+  +--+--+--+--+
|  |  |u |u |  |     | d| d|
+  +  +--+  +  +--+  +  +  +
|u |      u |  | d|  |  | d|
+--+--+--+--+  +--+  +  +--+
|u  u |u  u |  | d  d| d  d|
+--+--+--+--+  +--+--+--+--+
level 1         level 2


2x4x7 minimal
+--+--+--+--+--+--+--+
|           |        |
+           +        +
|           |        |
+        +--+        +
|        |           |
+        +           +
|        |           |
+--+--+--+--+--+--+--+
(2 levels deep)

...............................................................................

****
2*


2x4x7 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|  |u |u |   u |u    |  |    d| d   | d| d|  |
+  +--+--+     +     +  +     +     +--+--+  +
|  |           |     |  |     |           |  |
+  +--+--+--+--+--+  +  +  +--+--+--+--+--+  +
|     |           |  |  |  |           |     |
+     +     +--+--+  +  +  +--+--+     +     +
|   u |u    |u |u |  |  |  | d| d|    d| d   |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2

...............................................................................

*2*
***


2x4x7 minimal by Patrick Hamlyn
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|u  u  u |u  u  u |u |  | d  d  d| d  d  d| d|
+--+  +--+--+--+--+  +  +--+--+--+--+  +--+  +
|u |  |u |        |u |  | d|    d   |  |    d|
+  +--+--+        +  +  +  +        +--+--+  +
|u    |  |   u    |u |  | d|        | d|  | d|
+  +--+  +--+--+--+--+  +  +--+--+--+--+  +--+
|u |u  u  u |u  u  u |  | d| d  d  d| d  d  d|
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2


+--+--+--+     +--+--+--+     +--+--+--+
|u |u  u |     |ud|ud ud|     | d| d  d|
+  +--+--+     +  +--+  +     +  +--+--+
|u |     |     |ud   |  |     | d|     |
+--+     +--+  +--+--+--+--+  +--+     +--+
|u |u    |u |  |ud| d|u |ud|  | d|    d| d|
+  +     +  +  +  +--+--+  +  +  +     +  +
|u |     |u |  |ud   |   ud|  | d|     | d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3


3x4x7
+--+--+--+--+--+--+--+
|        |           |
+        +           +
|        |           |
+        +--+        +
|           |        |
+           +        +
|           |        |
+--+--+--+--+--+--+--+
(3 levels deep)

also: 3x6x14

...............................................................................

2**
***


+--+--+--+     +--+--+--+     +--+--+--+
|        |     |     |u |     |       d|
+        +     +     +--+     +        +
|      u |     |     | d|     |        |
+--+--+--+--+  +     +--+--+  +--+--+--+--+
|  |u |   u |  |    d|u |ud|  |       d| d|
+  +--+--+  +  +--+--+--+  +  +        +  +
|u  u  u |u |  | d  d  d|ud|  |        | d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3


3x4x7 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+--+
|        |           |
+        +           +
|        |           |
+        +--+        +
|           |        |
+           +        +
|           |        |
+--+--+--+--+--+--+--+
(3 levels deep)


same heptacube, allowing reflections

2x3x7 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|u       |u |u  u  u |  | d|       d| d  d  d|
+        +--+--+--+  +  +--+        +--+--+--+
|        |        |  |  |  |        |        |
+--+--+--+        +--+  +  +--+--+--+        +
|u  u  u |u       |u |  | d  d  d| d|       d|
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2

...............................................................................

22*
**


2x6x7 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|u    |u |u  u |   u |  | d|    d| d  d   | d|
+     +  +--+--+     +  +  +     +     +--+  +
|u    |u |     |   u |  | d|    d|     |  | d|
+  +--+--+     +--+  +  +--+--+  +--+--+  +--+
|  |u |   u  u |u |  |  |    d|  | d  d| d   |
+--+  +--+--+--+  +--+  +     +--+--+--+     +
|  |u |u  u    |u |  |  |    d| d  d|  | d   |
+  +--+     +--+--+  +  +--+  +--+--+  +--+--+
|u    |     |u |   u |  | d|  |     | d   | d|
+     +--+--+  +     +  +  +--+     +     +  +
|u    |u  u |u |   u |  | d|    d  d| d   | d|
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2

...............................................................................

2**
*2

allowing reflections


2x3x7 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|   u  u |u  u |   u |  |  | d  d| d  d   | d|
+--+--+  +--+  +--+  +  +  +  +--+  +--+--+  +
|u    |  |  |  |  |u |  | d|  |  |  |  |    d|
+  +--+--+  +--+  +  +  +  +--+  +--+  +--+--+
|u |   u  u |u  u |  |  | d   | d  d| d  d   |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2

...............................................................................

****
3

allowing reflections


+--+--+        +--+--+        +--+--+        +--+--+
|u |u |        |ud|ud|        |ud|ud|        | d| d|
+--+  +--+--+  +--+--+--+--+  +--+--+--+--+  +  +--+--+--+
|u |        |  | d         |  |         u |  |        | d|
+  +--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+  +
|  |        |  |           |  |           |  |        |  |
+  +  +--+--+  +  +--+--+--+  +--+--+--+  +  +--+--+  +  +
|  |u |u |u |  |u |ud|ud|ud|  |ud|ud|ud| d|  | d| d| d|  |
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4


4x4x7 minimal
+--+--+--+--+--+--+--+
|           |        |
+           +        +
|           |        |
+        +--+        +
|        |           |
+        +           +
|        |           |
+--+--+--+--+--+--+--+
(4 levels deep)

...............................................................................

2**
2*


4x6x7 minimal
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u    |u  u |u  u |  | d|u | d  d|ud  d|  |u  ud|u  u | d|u |  | d  d| d  d|    d|
+     +     +     +  +  +--+--+--+--+--+  +--+--+--+--+--+  +  +     +     +     +
|u    |     |     |  |ud|u  u |u  u |u |  | d| d  d| d  d|ud|  |     |     |    d|
+--+--+--+  +--+--+  +--+--+--+     +--+  +--+     +--+--+--+  +--+--+  +--+--+--+
|   u  u |  |   u |  |u | d  d|     |ud|  |ud|     |u  u | d|  | d   |  | d  d   |
+--+--+  +--+     +  +--+--+  +--+  +  +  +  +  +--+  +--+--+  +     +--+  +--+--+
|u    |u |u |   u |  | d|  | d| d|  | d|  |u |  |u |u |  |u |  | d   | d| d|    d|
+     +--+  +--+--+  +  +  +--+  +--+--+  +--+--+  +--+  +  +  +--+--+  +--+     +
|u    |  |u  u    |  |ud|     | d  d|u |  | d|u  u |     |ud|  |    d  d|  |    d|
+--+--+  +--+--+--+  +--+     +--+--+--+  +--+--+--+     +--+  +--+--+--+  +--+--+
|     |     |   u |  |u |u  u |u  u |ud|  |ud| d  d| d  d| d|  | d   |     |     |
+     +     +     +  +--+--+--+--+--+  +  +  +--+--+--+--+--+  +     +     +     +
|u  u |u  u |   u |  | d ud| d  d|u | d|  |u | d|u  u |ud u |  | d   | d  d| d  d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4


same heptacube, allowing reflections


+--+--+--+     +--+--+--+     +--+--+--+     +--+--+--+
|u |u  u |     |ud| d  d|     | d   |u |     |       d|
+--+     +     +  +--+--+     +     +  +     +--+     +
|  |     |     |u |     |     | d   |u |     |  |    d|
+  +  +--+--+  +--+     +--+  +--+--+--+--+  +  +--+--+--+
|u |  |   u |  | d|u  u |ud|  |u |ud  d| d|  | d| d|     |
+  +--+     +  +  +--+--+  +  +  +--+--+--+  +  +--+     +
|u  u |   u |  | d  d|u | d|  |u  u |ud ud|  | d  d| d  d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4


4x4x7 minimal
+--+--+--+--+--+--+--+
|        |           |
+        +           +
|        |           |
+        +--+        +
|           |        |
+           +        +
|           |        |
+--+--+--+--+--+--+--+
(4 levels deep)

also: 3x4x14, 3x4x21, 3x6x14, 3x6x21, 4x5x7, 5x6x7

...............................................................................

***2
  **

allowing reflections


4x4x7 minimal
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|u  u       |  | d  d|     |  |     |u  u |  |       d  d|
+  +--+--+--+  +--+--+     +  +     +--+--+  +--+--+--+  +
|  |  |  |u |  |          d|  |u          |  | d|  |  |  |
+--+  +  +--+  +--+--+--+--+  +--+--+--+--+  +--+  +  +--+
|u |  |  |u |  | d   |    d|  |u    |   u |  | d|  |  | d|
+--+  +  +  +  +     +--+  +  +  +--+     +  +  +  +  +--+
|     |u |u |  |     | d| d|  |u |u |     |  | d| d|     |
+     +  +--+  +  +--+  +  +  +  +  +--+  +  +--+  +     +
|   u |u    |  |  | d| d|  |  |  |u |u |  |  |    d| d   |
+--+--+--+--+  +  +--+--+  +  +  +--+--+  +  +--+--+--+--+
|   u |u |  |  |  |ud|ud|  |  |  |ud|ud|  |  |  | d| d   |
+--+  +--+  +  +--+  +--+--+  +--+--+  +--+  +  +--+  +--+
|u |u |u  u |  |ud| d| d ud|  |ud u |u |ud|  | d  d| d| d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4

...............................................................................

*2
*2*


4x4x7 minimal by Patrick Hamlyn
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|u  u    |u |  | d  d|    d|  |u    |u  u |  | d|    d  d|
+--+  +--+  +  +--+  +     +  +     +  +--+  +  +--+  +--+
|  |u |  |u |  |u | d|   ud|  |ud   |u | d|  | d|  | d|  |
+  +--+  +--+  +--+--+--+--+  +--+--+--+--+  +--+  +--+  +
|u  u |u  u |  | d  d| d  d|  |u  u |u  u |  | d  d| d  d|
+  +--+  +--+  +  +--+  +--+  +--+  +--+  +  +--+  +--+  +
|u |u |u |u |  | d| d| d| d|  |u |u |u |u |  | d| d| d| d|
+--+  +--+  +  +--+  +--+  +  +  +--+  +--+  +  +--+  +--+
|u  u |u  u |  | d  d| d  d|  |u  u |u  u |  | d  d| d  d|
+--+  +--+  +  +--+--+--+--+  +--+--+--+--+  +  +--+  +--+
|u |  |u |  |  |ud   | d|u |  | d|u |   ud|  |  | d|  | d|
+  +--+  +--+  +     +  +--+  +--+  +     +  +--+  +--+  +
|u |   u  u |  | d   | d  d|  |u  u |   u |  | d  d   | d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4


same heptacube, allowing reflections

2x6x7 minimal by Patrick Hamlyn
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|u  u |     |u  u |u |  | d  d   |    d  d| d|
+--+  +     +  +--+  +  +--+  +--+--+  +--+  +
|u |u |u  u |u |u  u |  | d| d| d  d| d| d  d|
+  +--+--+  +--+--+--+  +  +--+--+--+--+--+  +
|u  u |u |  |u  u |  |  | d  d| d|    d  d|  |
+  +--+  +--+  +--+  +  +--+--+  +--+  +--+--+
|  |u  u |  |u |u  u |  |  | d  d   | d| d  d|
+--+--+--+  +--+--+  +  +  +--+--+--+--+--+  +
|u  u |u |u  u |u |u |  | d  d| d| d  d| d| d|
+  +--+  +     +  +--+  +  +--+  +--+--+  +--+
|u |u  u |     |u  u |  | d| d  d   |    d  d|
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2


...............................................................................
Octacubes
...............................................................................


*
*******


1x2x8 minimal
+--+--+--+--+--+--+--+--+
|  |                    |
+  +--+--+--+--+--+--+  +
|                    |  |
+--+--+--+--+--+--+--+--+

also: 1x9x16, 1x12x44, 1x20x20
also: 3x7x8 by Andrew Clarke

...............................................................................

**
******


1x2x8 minimal
+--+--+--+--+--+--+--+--+
|     |                 |
+     +--+--+--+--+     +
|                 |     |
+--+--+--+--+--+--+--+--+

...............................................................................

***
*****


1x2x8 minimal
+--+--+--+--+--+--+--+--+
|        |              |
+        +--+--+        +
|              |        |
+--+--+--+--+--+--+--+--+

...............................................................................

***
*
****


1x4x4 minimal
+--+--+--+--+
|           |
+--+--+--+  +
|        |  |
+  +--+--+  +
|  |        |
+  +--+--+--+
|           |
+--+--+--+--+

...............................................................................

* *
* *
****


1x4x4 minimal
+--+--+--+--+
|           |
+--+  +--+  +
|  |  |  |  |
+  +  +  +  +
|  |  |  |  |
+  +--+  +--+
|           |
+--+--+--+--+

...............................................................................

  *
* **
****


1x4x4 minimal
+--+--+--+--+
|           |
+     +--+  +
|     |  |  |
+--+  +  +--+
|  |  |     |
+  +--+     +
|           |
+--+--+--+--+

...............................................................................

**
**
****


1x4x4 minimal
+--+--+--+--+
|           |
+--+--+     +
|     |     |
+     +     +
|     |     |
+     +--+--+
|           |
+--+--+--+--+

also: 1x5x16, 1x6x8, 1x7x16 by David Klarner
also: 4x6x6

...............................................................................

*
***
****


1x4x4 minimal
+--+--+--+--+
|           |
+--+        +
|  |        |
+  +--+--+  +
|        |  |
+        +--+
|           |
+--+--+--+--+

...............................................................................

  *
***
****


1x12x16 co-minimal by David Klarner
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|     |           |           |           |     |
+     +        +--+        +--+--+        +     +
|     |        |  |        |     |        |     |
+     +--+--+  +  +--+--+  +     +  +--+--+     +
|        |  |  |        |  |     |  |  |        |
+  +--+--+  +--+        +--+     +--+  +--+--+  +
|  |        |           |  |        |        |  |
+--+        +--+--+--+--+  +  +--+--+     +--+--+
|  |           |  |        |  |     |     |     |
+  +--+--+--+--+  +        +--+     +     +     +
|        |        |           |     |     |     |
+     +--+--+     +--+--+--+--+     +--+--+     +
|     |     |     |           |        |        |
+     +     +     +--+        +  +--+--+--+--+  +
|     |     |     |  |        |  |           |  |
+--+--+     +--+--+  +  +--+--+--+--+        +--+
|  |        |        |  |           |        |  |
+  +--+--+  +--+     +--+        +--+  +--+--+  +
|        |  |  |     |  |        |  |  |        |
+     +--+--+  +     +  +--+--+  +  +--+--+     +
|     |        |     |        |  |        |     |
+     +        +--+--+        +--+        +     +
|     |           |           |           |     |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+


4x6x8 co-minimal
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |u |   u  u  u |  | d| d|u |ud  d  d|  |u  u  ud| d|u |u |  | d  d  d   | d| d|
+  +  +--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+  +  +
|u |u |   u  u  u |  | d| d|u |ud  d  d|  |u  u  ud| d|u |u |  | d  d  d   | d| d|
+  +  +--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+  +  +
|u |u |     |  |  |  |ud|ud|     |u |u |  | d| d|     |ud|ud|  |  |  |     | d| d|
+  +  +     +  +  +  +--+--+     +--+--+  +--+--+     +--+--+  +  +  +     +  +  +
|  |  |     |u |u |  |u |u |     |ud|ud|  |ud|ud|     | d| d|  | d| d|     |  |  |
+--+--+     +  +  +  +--+--+     +  +  +  +  +  +     +--+--+  +  +  +     +--+--+
|  |        |u |u |  |  |        | d| d|  |u |u |        |  |  | d| d|        |  |
+  +--+--+  +  +  +  +  +--+--+  +  +  +  +  +  +  +--+--+  +  +  +  +  +--+--+  +
|        |  |u |u |  |        |  | d| d|  |u |u |  |        |  | d| d|  |        |
+     +--+--+--+--+  +     +--+--+--+--+  +--+--+--+--+     +  +--+--+--+--+     +
|     |   u  u  u |  |     |u |ud  d  d|  |u  u  ud| d|     |  | d  d  d   |     |
+     +--+--+--+--+  +     +--+--+--+--+  +--+--+--+--+     +  +--+--+--+--+     +
|     |   u  u  u |  |     |u |ud  d  d|  |u  u  ud| d|     |  | d  d  d   |     |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4

...............................................................................

*
****
***


4x7x8 minimal by Patrick Hamlyn
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|        |        |u |  |u  u  u |   u  u  ud|  |ud  d  d   | d  d  d|  | d|        |        |
+--+     +        +--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+        +     +--+
|u |     |           |  |ud u  u    |u  u  u |  | d  d  d|    d  d ud|  |           |     | d|
+--+     +  +--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+  +     +--+
|u |     |  |        |  |ud u  u    |u  u  u |  | d  d  d|    d  d ud|  |        |  |     | d|
+--+  +--+--+        +  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +        +--+--+  +--+
|u |  |  |           |  |ud u  u    |u  u  u |  | d  d  d|    d  d ud|  |           |  |  | d|
+--+--+  +--+--+--+  +  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +  +--+--+--+  +--+--+
|u |  |           |  |  |ud u  u    |u  u  u |  | d  d  d|    d  d ud|  |  |           |  | d|
+--+  +        +--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+        +  +--+
|     |        |  |u |  |u  u  u |   u  u  ud|  |ud  d  d   | d  d  d|  | d|  |        |     |
+     +--+--+--+  +--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+  +--+--+--+     +
|     |           |u |  |u  u  u |   u  u  ud|  |ud  d  d   | d  d  d|  | d|           |     |
+     +--+        +--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+        +--+     +
|        |        |u |  |u  u  u |   u  u  ud|  |ud  d  d   | d  d  d|  | d|        |        |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2                 level 3                 level 4

also: 1x36x40, 8x8x9, many others

...............................................................................

 *
***
****


5x8x12
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|           |u  u |u |u |  |u |u |u |   ud ud|ud|ud|  |ud|ud|ud u | d ud|ud|ud|
+--+        +--+--+  +  +  +--+--+--+--+--+--+  +  +  +  +  +--+--+--+--+  +  +
|u |        |u  u |u |u |  | d|  |u |   ud ud|ud|ud|  |u |u |ud u | d ud| d| d|
+  +--+  +--+--+--+--+--+  +  +  +--+--+--+--+  +  +  +--+--+--+--+--+--+--+--+
|u |u |  |  |u  u |     |  |ud|ud|u |   ud ud|  |  |  | d| d|ud u | d ud|u |u |
+  +  +--+  +--+--+     +  +  +  +--+--+--+--+--+--+  +--+  +--+--+--+--+  +--+
|u |u |  |     |        |  | d|ud|           |u |u |  |u |ud|           |ud| d|
+  +--+  +     +--+     +  +--+--+--+        +--+  +  +  +--+--+        +--+  +
|  |     |        |     |  |u |     |        |  |u |  |ud|     |        |  |ud|
+--+     +     +--+--+  +  +--+     +--+  +--+  +  +  +  +     +--+  +--+  +  +
|        |     |     |  |  |  |        |  |     |u |  |u |        |  |     | d|
+--+     +--+--+     +--+  +  +     +--+--+     +  +  +--+     +--+--+     +--+
|  |     |     |        |  |u |     |  |        |  |  | d|     |  |        |u |
+  +--+--+     +     +--+  +  +  +--+  +--+     +--+  +  +  +--+  +--+     +  +
|     |        |     |  |  |u |  |        |     |u |  |ud|  |        |     |ud|
+     +--+     +  +--+  +  +  +--+        +--+--+--+  +  +--+        +--+--+  +
|        |     |  |u |u |  |u |u |           |ud| d|  | d|ud|           |ud|u |
+     +--+--+  +--+  +  +  +--+--+--+--+--+--+  +  +  +--+  +--+--+--+--+  +--+
|     |u  u |  |  |u |u |  |  |  |ud ud   |u |ud|ud|  |u |u |ud  d|u  ud| d| d|
+--+--+--+--+--+  +--+  +  +  +  +--+--+--+--+  +  +  +--+--+--+--+--+--+--+--+
|u |u |u  u |        |u |  |ud|ud|ud ud   |u |  | d|  | d| d|ud  d|u  ud|u |u |
+  +  +--+--+        +--+  +  +  +--+--+--+--+--+--+  +  +  +--+--+--+--+  +  +
|u |u |u  u |           |  |ud|ud|ud ud   |u |u |u |  |ud|ud|ud  d|u  ud|ud|ud|
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 1                     level 2                    level 3

+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|ud|ud|ud ud   | d| d| d|  | d| d| d  d|           |
+  +  +--+--+--+--+--+--+  +  +  +--+--+        +--+
|ud|ud|ud ud   | d|  |u |  | d| d| d  d|        | d|
+  +  +--+--+--+--+  +  +  +--+--+--+--+--+  +--+  +
|  |  |ud ud   | d|ud|ud|  |     | d  d|  |  | d| d|
+--+--+--+--+--+--+  +  +  +     +--+--+  +--+  +  +
| d| d|           |ud|u |  |        |     |  | d| d|
+  +--+        +--+--+--+  +     +--+     +  +--+  +
| d|  |        |     | d|  |     |        |     |  |
+  +  +--+  +--+     +--+  +  +--+--+     +     +--+
| d|     |  |        |  |  |  |     |     |        |
+  +     +--+--+     +  +  +--+     +--+--+     +--+
|  |        |  |     | d|  |        |     |     |  |
+--+     +--+  +--+  +  +  +--+     +     +--+--+  +
| d|     |        |  | d|  |  |     |        |     |
+--+--+--+        +--+  +  +  +--+  +     +--+     +
|u |ud|           | d| d|  | d| d|  |     |        |
+  +  +--+--+--+--+--+--+  +  +  +--+  +--+--+     +
|ud|ud| d|   ud ud|  |  |  | d| d|  |  | d  d|     |
+  +  +--+--+--+--+  +  +  +  +--+  +--+--+--+--+--+
|u |  | d|   ud ud|ud|ud|  | d|        | d  d| d| d|
+--+--+--+--+--+--+  +  +  +--+        +--+--+  +  +
| d| d| d|   ud ud|ud|ud|  |           | d  d| d| d|
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
 level 4                    level 5

also: 1x41x48, others

...............................................................................

*  *
****
 **


4x4x4 minimal
+--+--+--+--+  +--+--+--+--+
|     |x    |  |  |   x |  |
+--+  +--+--+  +  +--+--+  +
|  |     |  |  |           |
+  +     +  +  +--+     +--+
|x |     |x |  |x |     |x |
+--+  +--+--+  +  +--+--+  +
|     |x    |  |  |   x |  |
+--+--+--+--+  +--+--+--+--+
levels 1, 4     levels 2, 3

...............................................................................

*
****
 ***


4x4x5 minimal
+--+--+--+--+--+  +--+--+--+--+--+
|  |u    |u    |  |    d|    d|  |
+  +--+--+--+--+  +--+--+--+--+  +
|           |  |  |  |           |
+--+        +  +  +  +        +--+
|u |        |u |  | d|        | d|
+  +--+--+--+--+  +--+--+--+--+  +
|  |u    |u    |  |    d|    d|  |
+--+--+--+--+--+  +--+--+--+--+--+
levels 1, 2, 3     level 4

...............................................................................

*    *
******


   +--+--+--+--+        +--+--+--+--+
   |u |u |u |u |        | d| d| d| d|
+--+--+--+--+--+--+  +--+  +  +  +  +--+
|u              u |  | d|  |  |  |  | d|
+--+--+--+--+--+--+  +--+  +  +  +  +--+
|u              u |  | d|  |  |  |  | d|
+--+--+--+--+--+--+  +--+  +  +  +  +--+
|u              u |  | d|  |  |  |  | d|
+--+--+--+--+--+--+  +--+  +  +  +  +--+
|u              u |  | d|  |  |  |  | d|
+--+--+--+--+--+--+  +--+  +  +  +  +--+
   |u |u |u |u |        | d| d| d| d|
   +--+--+--+--+        +--+--+--+--+
level 1               level 2


2x6x8 minimal by Andrew Clarke
+--+--+--+--+--+--+--+--+
|     |           |     |
+  +--+           +--+  +
|  |                 |  |
+  +                 +  +
|  |                 |  |
+  +                 +  +
|  |                 |  |
+  +                 +  +
|  |                 |  |
+  +--+           +--+  +
|     |           |     |
+--+--+--+--+--+--+--+--+
(2 levels deep)

...............................................................................

*  *
******


+--+--+  +--+--+     +--+--+  +--+--+
|  |x |  |  |x |     |   x |  |   x |
+  +--+--+  +--+--+  +--+--+--+--+--+--+
|                 |  |  |  |  |  |  |  |
+--+--+--+--+--+--+  +  +  +  +  +  +  +
|x |x |x |x |x |x |  |x |x |x |x |x |x |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
levels 1, 2, 4, 5     levels 3, 6


4x6x6 minimal
+--+--+--+--+--+--+
|                 |
+--+--+  +--+--+  +
|     |  |     |  |
+     +--+     +--+
|                 |
+                 +
|                 |
+--+--+--+--+--+--+
(6 levels deep)

...............................................................................

**
***
***


4x5x8 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|u  u |        |        |  | d  d   |        |u |u |  |        |        | d| d|
+--+--+        +        +  +--+--+--+        +  +  +  +        +        +  +  +
|u  u |        |        |  | d  d   |        |u |u |  |        |        | d| d|
+--+--+     +--+--+     +  +--+--+--+--+     +  +  +  +     +--+--+     +--+--+
|     |     |     |     |  |  |  |     |     |  |  |  |     |     |     |     |
+     +--+--+     +--+--+  +  +  +     +--+--+--+--+  +--+--+     +--+--+     +
|        |        |u  u |  |u |u |        |    d  d|  | d| d|        |        |
+        +        +--+--+  +  +  +        +--+--+--+  +  +  +        +        +
|        |        |u  u |  |u |u |        |    d  d|  | d| d|        |        |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 1                     levels 2, 3                level 4

...............................................................................

*
* **
****


4x6x8 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |u |u     u  u |  | d| d|ud|u | d  d|  |u  u | d|ud|u |u |  | d  d     d| d| d|
+  +  +--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+  +  +
|u |u |u     u  u |  | d| d|ud|u | d  d|  |u  u | d|ud|u |u |  | d  d     d| d| d|
+  +  +--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+  +  +
|  |  |     |u |u |  |u |u |     |ud|ud|  |ud|ud|     | d| d|  | d| d|     |  |  |
+  +  +     +  +  +  +--+--+     +--+--+  +--+--+     +--+--+  +  +  +     +  +  +
|u |u |     |  |  |  |ud|ud|     |u |u |  | d| d|     |ud|ud|  |  |  |     | d| d|
+--+--+--+  +  +  +  +--+--+--+  +--+--+  +--+--+  +--+--+--+  +  +  +  +--+--+--+
|        |  |u |u |  |        |  | d| d|  |u |u |  |        |  | d| d|  |        |
+  +--+--+  +  +  +  +  +--+--+  +  +  +  +  +  +  +--+--+  +  +  +  +  +--+--+  +
|  |        |u |u |  |  |        | d| d|  |u |u |        |  |  | d| d|        |  |
+  +--+--+--+--+--+  +  +--+--+--+--+--+  +--+--+--+--+--+  +  +--+--+--+--+--+  +
|     |u     u  u |  |     |ud|u | d  d|  |u  u | d|ud|     |  | d  d     d|     |
+     +--+--+--+--+  +     +--+--+--+--+  +--+--+--+--+     +  +--+--+--+--+     +
|     |u     u  u |  |     |ud|u | d  d|  |u  u | d|ud|     |  | d  d     d|     |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4

...............................................................................

**
 *  *
 ****


4x6x8 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |u |u        u |  | d| d|ud|u    | d|  |u |    d|ud|u |u |  | d        d| d| d|
+  +  +--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+  +  +
|  |  |u        u |  |  |  |ud|u    | d|  |u |    d|ud|  |  |  | d        d|  |  |
+  +  +--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+  +  +
|  |  |     |u |u |  |u |u |     |ud|ud|  |ud|ud|     | d| d|  | d| d|     |  |  |
+  +  +--+  +  +  +  +--+--+--+  +--+--+  +--+--+  +--+--+--+  +  +  +  +--+  +  +
|u |u |  |  |  |  |  |ud|ud|  |  |u |u |  | d| d|  |  |ud|ud|  |  |  |  |  | d| d|
+--+--+  +  +  +  +  +--+--+  +  +  +  +  +  +  +  +  +--+--+  +  +  +  +  +--+--+
|        |  |  |  |  |        |  |  |  |  |  |  |  |        |  |  |  |  |        |
+  +--+--+  +  +  +  +  +--+--+  +--+--+  +--+--+  +--+--+  +  +  +  +  +--+--+  +
|  |        |u |u |  |  |        | d| d|  |u |u |        |  |  | d| d|        |  |
+  +  +--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+  +  +
|  |  |u        u |  |  |  |ud|u    | d|  |u |    d|ud|  |  |  | d        d|  |  |
+  +--+--+--+--+--+  +  +--+--+--+--+--+  +--+--+--+--+--+  +  +--+--+--+--+--+  +
|     |u        u |  |     |ud|u    | d|  |u |    d|ud|     |  | d        d|     |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4

...............................................................................

***
  *
  ****


4x6x8 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|  |  |u          |  |  |  |ud|u       |  |       d|ud|  |  |  |          d|  |  |
+  +  +--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+  +  +
|  |  |u          |  |  |  |ud|u       |  |       d|ud|  |  |  |          d|  |  |
+  +  +--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+  +  +
|  |  |  |  |u |u |  |u |u |  |  |ud|ud|  |ud|ud|  |  | d| d|  | d| d|  |  |  |  |
+  +  +  +  +  +  +  +--+--+  +  +--+--+  +--+--+  +  +--+--+  +  +  +  +  +  +  +
|u |u |  |  |  |  |  |ud|ud|  |  |u |u |  | d| d|  |  |ud|ud|  |  |  |  |  | d| d|
+--+--+  +  +  +  +  +--+--+  +  +  +  +  +  +  +  +  +--+--+  +  +  +  +  +--+--+
|        |  |  |  |  |        |  |  |  |  |  |  |  |        |  |  |  |  |        |
+  +--+--+  +  +  +  +  +--+--+  +  +  +  +  +  +  +--+--+  +  +  +  +  +--+--+  +
|  |        |  |  |  |  |        |  |  |  |  |  |        |  |  |  |  |        |  |
+  +  +--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+  +  +
|  |  |u          |  |  |  |ud|u       |  |       d|ud|  |  |  |          d|  |  |
+  +  +--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+  +  +
|  |  |u          |  |  |  |ud|u       |  |       d|ud|  |  |  |          d|  |  |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4

...............................................................................

*
***
  *
  ***


4x6x8 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |u |u       |u |  | d| d|ud|u      d|  |u      d|ud|u |u |  | d|       d| d| d|
+--+--+--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+--+--+
|  |  |u       |u |  |  |  |ud|u      d|  |u      d|ud|  |  |  | d|       d|  |  |
+  +  +--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+  +  +
|  |  |     |u |u |  |u |u |     |ud|ud|  |ud|ud|     | d| d|  | d| d|     |  |  |
+  +  +  +--+  +  +  +--+--+  +--+--+--+  +--+--+--+  +--+--+  +  +  +--+  +  +  +
|u |u |  |  |  |  |  |ud|ud|  |  |u |u |  | d| d|  |  |ud|ud|  |  |  |  |  | d| d|
+--+--+  +  +  +  +  +--+--+  +  +  +  +  +  +  +  +  +--+--+  +  +  +  +  +--+--+
|        |  |  |  |  |        |  |  |  |  |  |  |  |        |  |  |  |  |        |
+  +--+--+  +--+--+  +  +--+--+  +  +  +  +  +  +  +--+--+  +  +--+--+  +--+--+  +
|  |        |u |u |  |  |        | d| d|  |u |u |        |  |  | d| d|        |  |
+  +  +--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+  +  +
|  |  |u       |u |  |  |  |ud|u      d|  |u      d|ud|  |  |  | d|       d|  |  |
+--+  +--+--+--+--+  +--+  +--+--+--+--+  +--+--+--+--+  +--+  +--+--+--+--+  +--+
|     |u       |u |  |     |ud|u      d|  |u      d|ud|     |  | d|       d|     |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4

...............................................................................

**
***
  *
  **


4x6x8 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |u |u    |u  u |  | d| d|ud|u   d  d|  |u  u   d|ud|u |u |  | d  d|    d| d| d|
+  +  +--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+  +  +
|u |u |u    |u  u |  | d| d|ud|u   d  d|  |u  u   d|ud|u |u |  | d  d|    d| d| d|
+--+--+--+--+--+--+  +  +  +--+--+--+--+  +--+--+--+--+  +  +  +--+--+--+--+--+--+
|  |  |     |u |u |  |u |u |     |ud|ud|  |ud|ud|     | d| d|  | d| d|     |  |  |
+  +  +     +  +  +  +--+--+     +--+--+  +--+--+     +--+--+  +  +  +     +  +  +
|u |u |     |  |  |  |ud|ud|     |u |u |  | d| d|     |ud|ud|  |  |  |     | d| d|
+--+--+  +--+--+--+  +--+--+  +--+  +  +  +  +  +--+  +--+--+  +--+--+--+  +--+--+
|        |  |u |u |  |        |  | d| d|  |u |u |  |        |  | d| d|  |        |
+  +--+--+  +  +  +  +  +--+--+  +  +  +  +  +  +  +--+--+  +  +  +  +  +--+--+  +
|  |        |u |u |  |  |        | d| d|  |u |u |        |  |  | d| d|        |  |
+--+  +--+--+--+--+  +--+  +--+--+--+--+  +--+--+--+--+  +--+  +--+--+--+--+  +--+
|     |u    |u  u |  |     |ud|u   d  d|  |u  u   d|ud|     |  | d  d|    d|     |
+     +--+--+--+--+  +     +--+--+--+--+  +--+--+--+--+     +  +--+--+--+--+     +
|     |u    |u  u |  |     |ud|u   d  d|  |u  u   d|ud|     |  | d  d|    d|     |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4

...............................................................................

* **
*****


+--+--+--+--+  +--+--+--+--+
|x |     |x |  |x    |   x |
+--+  +--+--+  +--+--+--+--+
|x |  |x |     |x    |x |
+--+  +--+     +--+--+  +
|x |     |     |x    |  |
+--+     +     +--+--+--+
|x |     |     |x    |  |
+--+  +--+     +--+--+  +
|x |  |x |     |x    |x |
+--+--+--+     +--+--+--+
levels 1, 4     levels 2, 3, 5


   +--+--+        +--+--+
   |  |x |        |   x |
+--+  +--+--+  +--+--+--+--+
|x |     |x |  |x    |   x |
+--+     +--+  +--+--+--+--+
|x |     |     |x    |  |
+--+  +--+     +--+--+  +
|x |  |x |     |x    |x |
+--+  +--+--+  +--+--+--+--+
|x |     |x |  |x    |   x |
+--+--+--+--+  +--+--+--+--+
levels 1, 4     levels 2, 3, 5


5x5x8 minimal by Andrew Clarke
+--+--+--+--+--+--+--+--+
|           |     |     |
+        +--+     +--+  +
|        |           |  |
+        +        +--+  +
|        |        |     |
+        +        +     +
|        |        |     |
+        +        +--+  +
|        |           |  |
+--+--+--+--+--+--+--+--+
(5 levels deep)

also: 5x6x8, 5x8x8

...............................................................................

*
*
******


4x7x8 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|        |        |u |  |u                |ud|  |ud|                d|  | d|        |        |
+  +--+--+--+--+  +--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+  +--+--+--+--+  +
|  |        |  |  |u |  |u                |ud|  |ud|                d|  | d|  |  |        |  |
+  +  +--+--+  +  +--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+  +  +--+--+  +  +
|  |  |  |  |  |  |u |  |u                |ud|  |ud|                d|  | d|  |  |  |  |  |  |
+  +  +  +  +  +  +--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+  +  +  +  +  +  +
|  |  |  |  |  |  |u |  |u                |ud|  |ud|                d|  | d|  |  |  |  |  |  |
+  +  +  +  +  +  +--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+  +  +  +  +  +  +
|  |  |  |  |  |  |u |  |u                |ud|  |ud|                d|  | d|  |  |  |  |  |  |
+  +  +  +  +  +  +--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+  +  +  +  +  +  +
|  |  |  |  |  |  |u |  |u                |ud|  |ud|                d|  | d|  |  |  |  |  |  |
+--+  +  +  +  +--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+  +  +  +  +--+
|u |  |  |  |        |  |ud|               u |  | d               |ud|  |        |  |  |  | d|
+--+--+  +  +--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+  +  +--+--+
|        |        |u |  |u                |ud|  |ud|                d|  | d|        |        |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2                 level 3                 level 4

also: 6x6x8

...............................................................................

* *
****
 * *


4x7x8 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|  |x    |x    |x    |  |   x |   x |   x |  |
+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +
|x |  |x    |x    |x |  |x |   x |   x |  |x |
+--+  +--+--+--+--+  +  +  +--+--+--+--+  +--+
|  |x |  |x    |x |  |  |  |x |   x |  |x |  |
+  +--+  +--+--+  +--+  +--+  +--+--+  +--+  +
|           |  |  |  |  |  |  |  |           |
+--+  +--+  +  +--+  +  +  +--+  +  +--+  +--+
|x |  |x |  |x |  |x |  |x |  |x |  |x |  |x |
+  +--+  +--+--+  +--+  +--+  +--+--+  +--+  +
|  |x |  |x    |x |  |  |  |x |   x |  |x |  |
+--+  +--+--+--+--+  +  +  +--+--+--+--+  +--+
|x |  |x    |x    |x |  |x |   x |   x |  |x |
+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +
|  |x    |x    |x    |  |   x |   x |   x |  |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
levels 1, 3              levels 2, 4

...............................................................................

* * *
*****


+--+--+--+--+--+--+  +--+--+--+--+--+--+
|   x |   x |   x |  |  |x |  |x |  |x |
+--+--+--+--+--+--+  +  +--+  +--+  +--+
|  |  |  |  |  |     |              |
+  +  +  +  +  +     +--+--+--+--+--+
|x |x |x |x |x |     |x |x |x |x |x |
+--+--+--+--+--+     +--+--+--+--+--+
levels 1, 3, 5        levels 2, 4


+--+--+--+--+--+--+  +--+--+--+--+--+--+
|   x |   x |   x |  |  |x |  |x |  |x |
+--+--+--+--+--+--+  +  +--+  +--+  +--+
|  |  |  |  |   x |  |              |x |
+  +  +  +  +--+--+  +--+--+--+--+--+--+
|x |x |x |x |        |x |x |x |x |
+--+--+--+--+        +--+--+--+--+
levels 1, 3, 5        levels 2, 4


            +--+              +--+
            |x |              |x |
+--+--+--+--+  +  +--+--+--+--+--+
|   x |   x |  |  |  |x |  |x |  |
+--+--+--+--+--+  +  +--+  +--+  +
|  |  |  |  |  |  |              |
+  +  +  +  +  +  +--+--+--+--+--+
|x |x |x |x |x |  |x |x |x |x |x |
+--+--+--+--+--+  +--+--+--+--+--+
levels 1, 3, 5     levels 2, 4


3x5x16 co-minimal
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                 |              |              |
+              +--+  +--+  +--+  +              +
|              |  |  |  |  |  |  |              |
+              +  +--+  +--+  +--+              +
|              |              |                 |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
(5 levels deep)


5x6x8 co-minimal
+--+--+--+--+--+--+--+--+
|                 |     |
+                 +     +
|                 |     |
+           +--+--+     +
|           |  |        |
+--+--+--+--+  +        +
|              |        |
+              +        +
|              |        |
+              +        +
|              |        |
+--+--+--+--+--+--+--+--+
(5 levels deep)

also: 5x8x8

...............................................................................

** *
*****


+--+--+--+--+--+--+  +--+--+--+--+--+--+
|x |  |x |     |x |  |x    |x    |   x |
+--+  +--+     +--+  +--+--+--+--+--+--+
|              |     |  |  |  |  |  |
+--+--+--+--+--+     +  +  +  +  +  +
|x |x |x |x |x |     |x |x |x |x |x |
+--+--+--+--+--+     +--+--+--+--+--+
levels 1, 3           levels 2, 4, 5


+--+--+--+--+--+--+  +--+--+--+--+--+--+
|x |  |x |     |x |  |x    |x    |   x |
+--+  +--+     +--+  +--+--+--+--+--+--+
|              |x |  |  |  |  |  |   x |
+--+--+--+--+--+--+  +  +  +  +  +--+--+
|x |x |x |x |        |x |x |x |x |
+--+--+--+--+        +--+--+--+--+
levels 1, 3           levels 2, 4, 5


            +--+              +--+
            |x |              |x |
+--+--+--+--+--+  +--+--+--+--+  +
|x |  |x |     |  |x    |x    |  |
+--+  +--+     +  +--+--+--+--+--+
|              |  |  |  |  |  |  |
+--+--+--+--+--+  +  +  +  +  +  +
|x |x |x |x |x |  |x |x |x |x |x |
+--+--+--+--+--+  +--+--+--+--+--+
levels 1, 3        levels 2, 4, 5


3x5x16 co-minimal
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                 |              |              |
+              +--+--+  +--+     +              +
|              |     |  |  |     |              |
+              +     +--+  +--+--+              +
|              |              |                 |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
(5 levels deep)


5x6x8 co-minimal
+--+--+--+--+--+--+--+--+
|                 |     |
+                 +     +
|                 |     |
+           +--+--+     +
|           |  |        |
+--+--+--+--+  +        +
|              |        |
+              +        +
|              |        |
+              +        +
|              |        |
+--+--+--+--+--+--+--+--+
(5 levels deep)

also: 5x8x8

...............................................................................

*  **
*****


4x6x8 minimal
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |u  u        u |  | d| d  d|u |u | d|  |u |u  u | d| d|u |  | d| d  d        d|
+  +--+--+--+--+--+  +  +--+--+  +  +--+  +  +--+--+--+--+--+  +  +--+--+--+--+--+
|u |              |  | d|u  u |  |  |u |  |u | d  d        d|  | d|              |
+--+     +--+--+  +  +  +--+--+  +  +--+  +  +--+--+--+--+--+  +--+     +--+--+  +
|  |     |     |  |  |  |u  u |  |  |u |  |  | d  d        d|  |  |     |     |  |
+  +--+--+     +--+  +  +--+--+  +  +--+  +  +--+--+--+--+--+  +  +--+--+     +--+
|              |u |  |  |u |u |u |u | d|  |  | d| d| d| d|u |  |              | d|
+--+--+--+--+--+--+  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +--+--+--+--+--+--+
|u |              |  | d|u |u |u |u |  |  |u | d| d| d| d|  |  | d|              |
+--+     +--+--+  +  +--+  +  +--+--+  +  +--+--+--+--+--+  +  +--+     +--+--+  +
|  |     |     |  |  |u |  |  |u  u |  |  | d        d  d|  |  |  |     |     |  |
+  +--+--+     +--+  +--+  +  +--+--+  +  +--+--+--+--+--+  +  +  +--+--+     +--+
|              |u |  |u |  |  |u  u | d|  | d        d  d|u |  |              | d|
+--+--+--+--+--+  +  +--+  +  +--+--+  +  +--+--+--+--+--+  +  +--+--+--+--+--+  +
|u        u  u |u |  | d|u |u | d  d| d|  |u | d| d|u  u |u |  | d        d  d| d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4


also: 3x5x16, 4x5x12, 5x6x8, 5x8x8, 5x8x10

...............................................................................

* *
******


+--+--+--+--+        +--+--+--+--+
|  |x |  |x |        |   x |   x |
+  +--+  +--+--+--+  +--+--+--+--+--+--+
|                 |  |  |  |  |  |  |  |
+--+--+--+--+--+--+  +  +  +  +  +  +  +
|x |x |x |x |x |x |  |x |x |x |x |x |x |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
levels 1, 2, 3, 5     levels 4, 6


+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|                 |x |  |  |  |  |     |   x |
+--+--+--+  +--+  +--+  +  +  +  +  +--+--+--+
|x |x |x |  |x |  |x |  |x |x |x |  |x    |x |
+--+--+--+--+--+--+--+  +--+--+--+  +--+--+  +
|x |                 |  |x    |  |     |  |  |
+--+  +--+  +--+--+--+  +--+--+  +  +--+  +--+
|x |  |x |  |x |x |     |x    |x |  |x |x |
+--+--+--+--+--+--+--+  +--+--+--+  +  +--+--+
|                 |x |  |  |  |  |  |  |   x |
+--+--+--+  +--+  +--+  +  +  +  +  +--+--+--+
|x |x |x |  |x |  |     |x |x |x |  |x    |
+--+--+--+--+--+--+     +--+--+--+--+--+--+
levels 1, 2, 3, 5        levels 4, 6


3x6x16
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|           |                 |                 |
+           +--+--+--+  +--+  +                 +
|                 |  |  |  |  |                 |
+                 +  +--+  +--+--+--+           +
|                 |                 |           |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
(6 levels deep)


6x6x8
+--+--+--+--+--+--+--+--+
|                    |  |
+                    +  +
|                    |  |
+                    +  +
|                    |  |
+                 +--+  +
|                 |     |
+                 +--+  +
|                    |  |
+                 +--+  +
|                 |     |
+--+--+--+--+--+--+--+--+
(6 levels deep)

...............................................................................

  **
******


   +--+--+--+--+        +--+--+--+--+
   |x |     |x |        |x    |   x |
+--+--+     +--+--+  +--+--+--+--+--+--+
|                 |  |  |  |  |  |  |  |
+--+--+--+--+--+--+  +  +  +  +  +  +  +
|x |x |x |x |x |x |  |x |x |x |x |x |x |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
levels 1, 2, 5, 6     levels 3, 4


6x6x8 minimal
+--+--+--+--+--+--+--+--+
|  |                 |  |
+  +                 +  +
|  |                 |  |
+  +--+           +--+  +
|     |           |     |
+     +--+--+--+--+     +
|     |           |     |
+  +--+           +--+  +
|  |                 |  |
+  +                 +  +
|  |                 |  |
+--+--+--+--+--+--+--+--+
(6 levels deep)

also: 6x8x8

...............................................................................

 * *
******


+--+--+--+--+        +--+--+--+--+
|x |  |x |  |        |x    |x    |
+--+  +--+  +--+--+  +--+--+--+--+--+--+
|                 |  |  |  |  |  |  |  |
+--+--+--+--+--+--+  +  +  +  +  +  +  +
|x |x |x |x |x |x |  |x |x |x |x |x |x |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
levels 1, 3, 5, 6     levels 2, 4


   +--+--+--+--+        +--+--+--+--+
   |  |x |  |x |        |   x |   x |
+--+  +--+  +--+--+  +--+--+--+--+--+--+
|                 |  |  |  |  |  |  |  |
+--+--+--+--+--+--+  +  +  +  +  +  +  +
|x |x |x |x |x |x |  |x |x |x |x |x |x |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
levels 1, 3, 5, 6     levels 2, 4


3x6x16
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|           |                 |                 |
+           +--+--+  +--+  +--+                 +
|                 |  |  |  |  |                 |
+                 +--+  +--+  +--+--+           +
|                 |                 |           |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
(6 levels deep)


6x6x8
+--+--+--+--+--+--+--+--+
|  |                 |  |
+  +--+  +--+  +--+--+  +
|     |  |  |  |  |     |
+  +--+--+  +--+  +--+  +
|  |                 |  |
+  +--+--+--+--+--+--+  +
|     |           |     |
+  +--+           +--+  +
|  |                 |  |
+  +                 +  +
|  |                 |  |
+--+--+--+--+--+--+--+--+
(6 levels deep)

...............................................................................

 *  *
******


+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
|u |  |u |  |u |  |ud   |ud|   ud|  |ud|  |ud|  |ud|  |ud|  |ud|  |ud|  |ud   |ud|   ud|  | d|  | d|  | d|
+--+  +--+  +--+  +--+--+  +--+--+  +--+  +--+  +--+  +--+  +--+  +--+  +--+--+  +--+--+  +--+  +--+  +--+
   |u |     |        | d|  |u |        |     | d|        |     |u |        |u |  | d|        | d|     |
   +  +--+  +--+     +--+--+--+--+     +  +--+  +--+     +  +--+  +--+     +--+--+--+--+     +  +--+  +--+
   |  |u |  |u |     |   ud|   ud|     |  |ud|  |ud|     |  |ud|  |ud|     |   ud|   ud|     |  | d|  | d|
   +  +--+  +--+     +--+--+--+--+     +  +--+  +--+     +  +--+  +--+     +--+--+--+--+     +  +--+  +--+
   |  |u |  |u |     |   ud|   ud|     |  |ud|  |ud|     |  |ud|  |ud|     |   ud|   ud|     |  | d|  | d|
   +  +--+  +--+     +--+--+--+--+     +  +--+  +--+     +  +--+  +--+     +--+--+--+--+     +  +--+  +--+
   |u |     |        | d|  |u |        |     | d|        |     |u |        |u |  | d|        | d|     |
+--+  +--+  +--+  +--+--+  +--+--+  +--+  +--+  +--+  +--+  +--+  +--+  +--+--+  +--+--+  +--+  +--+  +--+
|u |  |u |  |u |  |ud   |ud|   ud|  |ud|  |ud|  |ud|  |ud|  |ud|  |ud|  |ud   |ud|   ud|  | d|  | d|  | d|
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
level 1            level 2           level 3           level 4           level 5           level 6


   +--+--+--+--+        +--+--+--+--+
   |  |x |x |  |        |   x |x    |
+--+  +--+--+  +--+  +--+--+--+--+--+--+
|                 |  |  |  |  |  |  |  |
+--+--+--+--+--+--+  +  +  +  +  +  +  +
|x |x |x |x |x |x |  |x |x |x |x |x |x |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
levels 1, 3, 4, 6     levels 2, 5


6x6x8 minimal
+--+--+--+--+--+--+--+--+
|     |              |  |
+     +--+        +--+  +
|        |        |     |
+        +        +--+  +
|        |           |  |
+        +           +  +
|        |           |  |
+        +        +--+  +
|        |        |     |
+     +--+        +--+  +
|     |              |  |
+--+--+--+--+--+--+--+--+
(6 levels deep)

...............................................................................

 ***
*****


      +--+--+           +--+--+
      |x |x |           |x |x |
+--+--+--+--+     +--+--+  +  +
|x |        |     |x    |  |  |
+--+        +--+  +--+--+--+--+--+
|              |  |  |  |  |  |  |
+--+--+--+--+--+  +  +  +  +  +  +
|x |x |x |x |x |  |x |x |x |x |x |
+--+--+--+--+--+  +--+--+--+--+--+
levels 1, 5        levels 2, 3, 4


5x8x8 minimal
+--+--+--+--+--+--+--+--+
|        |              |
+        +              +
|        |              |
+        +--+           +
|           |           |
+           +     +--+--+
|           |     |     |
+     +--+--+--+--+     +
|     |     |           |
+--+--+     +           +
|           |           |
+           +--+        +
|              |        |
+              +        +
|              |        |
+--+--+--+--+--+--+--+--+
(5 levels deep)

...............................................................................

 *
*******


+--+--+                    +--+--+
|x |  |                    |x    |
+--+  +--+--+--+--+--+     +--+--+--+--+--+--+--+
|                    |     |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+     +  +  +  +  +  +  +  +
|x |x |x |x |x |x |x |     |x |x |x |x |x |x |x |
+--+--+--+--+--+--+--+     +--+--+--+--+--+--+--+
levels 1, 3, 4, 5, 6, 7     level 2


3x7x16 by Andrew Clarke
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|     |                    |                    |
+     +--+--+--+--+--+  +--+                    +
|                    |  |  |                    |
+                    +--+  +--+--+--+--+--+     +
|                    |                    |     |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
(7 levels deep)

...............................................................................

 **
******


         +--+--+              +--+--+
         |x |x |              |x |x |
   +--+--+--+--+        +--+--+  +  +
   |x |x |     |        |x |x |  |  |
+--+--+--+     +--+  +--+  +  +--+--+--+
|                 |  |  |  |  |  |  |  |
+--+--+--+--+--+--+  +  +--+--+  +  +  +
|x |     |x |x |x |  |x |     |x |x |x |
+--+     +--+--+--+  +--+     +--+--+--+
levels 1, 4, 5, 6     levels 2, 3


      +--+                 +--+
      |x |                 |x |
+--+--+--+           +--+--+  +
|x |     |           |x    |  |
+--+     +--+--+--+  +--+--+--+--+--+--+
|                 |  |  |  |  |  |  |  |
+--+--+--+--+--+--+  +  +  +  +  +  +  +
|x |x |x |x |x |x |  |x |x |x |x |x |x |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
levels 1, 4, 5, 6     levels 2, 3


6x6x8
+--+--+--+--+--+--+--+--+
|  |                 |  |
+  +--+     +--+--+--+  +
|     |     |     |     |
+     +--+--+     +     +
|     |           |     |
+  +--+           +--+  +
|  |                 |  |
+  +  +--+--+        +  +
|  |  |     |        |  |
+  +--+     +--+--+--+  +
|  |                 |  |
+--+--+--+--+--+--+--+--+
(6 levels deep)


6x8x8
+--+--+--+--+--+--+--+--+
|                 |     |
+                 +     +
|                 |     |
+--+--+--+        +     +
|        |        |     |
+        +  +--+--+     +
|        |  |           |
+        +--+--+        +
|           |  |        |
+     +--+--+  +        +
|     |        |        |
+     +        +--+--+--+
|     |                 |
+     +                 +
|     |                 |
+--+--+--+--+--+--+--+--+
(6 levels deep)

also: 4x6x16

...............................................................................

  *
*******


7x7x8
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|  |x |  |x |  |x |  |x |  |   x |   x |   x |   x |
+  +--+  +--+  +--+  +--+  +--+--+--+--+--+--+--+--+
|  |x |  |x |  |x |  |x |  |   x |  |x    |x    |x |
+  +--+  +--+  +--+  +--+  +--+--+  +--+--+--+--+  +
|     |     |     |     |  |                    |  |
+  +--+  +--+  +--+  +--+  +--+--+--+--+--+--+--+--+
|  |x |  |x |  |x |  |x |  |   x |   x |   x |   x |
+  +--+  +--+  +--+  +--+  +--+--+--+--+--+--+--+--+
|  |x |  |x |  |x |  |x |  |   x |   x |   x |   x |
+  +--+  +--+  +--+  +--+  +--+--+--+--+--+--+--+--+
|  |x |  |x |  |x |  |x |  |   x |   x |   x |   x |
+  +--+  +--+  +--+  +--+  +--+--+--+--+--+--+--+--+
|  |x |  |x |  |x |  |x |  |   x |   x |   x |   x |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
levels 1, 2, 4, 5, 6, 7     level 3

...............................................................................

*
*
*
*****


6x6x8 minimal by Patrick Hamlyn
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|              |u |  |u |           |ud|  |ud|           |ud|
+  +--+--+--+--+--+  +  +  +--+--+--+--+  +--+  +--+--+--+--+
|  |              |  |  |  |           |  |u |  |           |
+  +  +--+--+--+--+  +  +  +--+--+--+  +  +--+  +--+--+--+  +
|  |  |u          |  |  |  |ud|u |  |  |  |  |  |ud|ud|u |  |
+  +  +--+--+--+--+  +  +  +--+--+  +  +  +  +  +--+--+  +  +
|  |  |u          |  |  |  |ud|u |  |  |  |  |  |ud|ud|  |  |
+--+  +--+--+--+--+  +--+  +--+--+  +  +  +  +  +--+--+  +  +
|  |  |u          |  |  |  |ud|u |  |  |  |  |  |ud|ud|  |  |
+  +--+--+--+--+--+  +  +--+--+--+  +  +  +  +--+--+--+  +  +
|  |u |u          |  |  |ud|ud|u |  |  |  |  |ud|ud|ud|  |  |
+  +--+--+--+--+--+  +  +--+--+--+  +--+  +  +--+--+--+  +--+
|  |            u |  |  |           |ud|  |           |  |ud|
+  +--+--+--+--+--+  +  +--+--+--+--+--+  +--+--+--+--+--+--+
|              |u |  |              |ud|  |u             |ud|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3

+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|ud|             d|  |ud|              |  | d|              |
+--+--+--+--+--+--+  +--+--+--+--+--+  +  +--+--+--+--+--+  +
|ud|  |           |  |ud|           |  |  | d            |  |
+--+  +--+--+--+  +  +--+  +--+--+--+  +  +--+--+--+--+--+  +
|  |  |ud|ud|ud|  |  |  |  | d|ud|ud|  |  |          d| d|  |
+  +  +--+--+--+  +  +  +  +--+--+--+  +  +--+--+--+--+--+  +
|  |  |ud|ud|  |  |  |  |  | d|ud|  |  |  |          d|  |  |
+  +  +--+--+  +  +  +  +  +--+--+  +--+  +--+--+--+--+  +--+
|  |  |ud|ud|  |  |  |  |  | d|ud|  |  |  |          d|  |  |
+  +  +--+--+  +  +  +  +  +--+--+  +  +  +--+--+--+--+  +  +
|  | d|ud|ud|  |  |  |  |  | d|ud|  |  |  |          d|  |  |
+  +--+--+--+  +--+  +  +--+--+--+  +  +  +--+--+--+--+  +  +
|           |  | d|  |           |  |  |  |              |  |
+--+--+--+--+  +--+  +--+--+--+--+  +  +  +--+--+--+--+--+  +
|ud|           |ud|  |ud|           | d|  | d|              |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 4               level 5              level 6


               +--+--+                    +--+--+                    +--+--+
               |u |u |                    |ud|ud|                    | d| d|
               +--+--+                    +--+--+                    +  +  +
               |  |u |                    |  | d|                    |  |  |
               +  +--+                    +  +  +                    +  +  +
               |  |  |                    |  |  |                    |  |  |
               +  +  +                    +  +  +                    +  +  +
               |  |  |                    |  |  |                    |  |  |
+--+--+--+--+--+  +  +--+  +--+--+--+--+--+  +  +--+  +--+--+--+--+--+--+--+--+
|u |              |  |u |  |ud|              |  |ud|  | d         |          d|
+--+--+--+--+--+--+  +--+  +--+--+--+--+--+--+  +--+  +--+--+--+--+--+--+--+--+
|u |u |              |u |  |ud| d            |  |ud|  | d         |          d|
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
levels 1, 2, 3              level 4                    level 5


5x8x10
+--+--+--+--+--+--+--+--+--+--+
|     |  |              |     |
+     +  +  +--+--+--+--+     +
|     |  |  |                 |
+     +  +  +                 +
|     |  |  |                 |
+     +  +  +--+--+--+--+     +
|     |  |  |           |     |
+     +  +--+--+--+--+  +     +
|     |           |  |  |     |
+     +--+--+--+--+  +  +     +
|                 |  |  |     |
+                 +  +  +     +
|                 |  |  |     |
+     +--+--+--+--+  +  +     +
|     |              |  |     |
+--+--+--+--+--+--+--+--+--+--+
(5 levels deep)

also: 5x6x12 by Patrick Hamlyn
also: 5x8x12, 5x8x14

...............................................................................

   *
*******


7x7x16
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|                    |  |  |  |  |u |  |  |  |  |          d         |  |  |  |  |u |  |  |  |
+--+--+--+  +--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|u |u |u |  |u |u |u |  | d| d| d|u | d| d| d|  |u |u |u |ud|u |u |u |  | d| d| d|ud| d| d| d|
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  level 2                 level 3                 level 4

+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|          d         |  |  |  |  |u |  |  |  |  |          d         |  |  |  |  |u |  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|u |u |   ud|u |u |u |  | d| d|u |ud| d| d| d|  |u |u | d|ud|u |u |u |  | d| d|u | d| d| d| d|
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 5                  level 6                 level 7                 level 8

+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|          d         |  |  |  |  |u |  |  |  |  |          d         |  |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +  +  +  +  +
|u |u | d|u |u |u |u |  | d| d|u |ud| d| d| d|  |u |u | d|ud|u |u |u |  | d| d|u |ud| d| d| d|
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 9                  level 10                level 11                level 12

+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|u |u | d|ud|u |u |u |  | d| d|u |ud| d| d| d|  |u |u | d| d|u |u |u |  | d| d|     | d| d| d|
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +  +--+--+--+--+--+--+--+  +  +  +  +--+  +  +  +
|         u          |  |  |  |  | d|  |  |  |  |         u          |  |  |  |  | d|  |  |  |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 13                 level 14                level 15                level 16

...............................................................................

*   *
******


+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|x |                 |  |x    |  |  |  |     |
+--+  +--+--+--+  +--+  +--+--+  +  +  +  +--+
|x |  |x |x |x |  |     |x    |x |x |x |  |
+--+--+--+--+--+--+--+  +--+--+--+--+--+  +--+
|x |                 |  |x    |  |  |  |  |  |
+--+  +--+--+--+  +--+  +--+--+  +  +  +  +  +
|x |  |x |x |x |  |x |  |x    |x |x |x |  |x |
+--+--+--+--+--+--+--+  +--+--+--+--+--+  +--+
|x |                 |  |x    |  |  |  |     |
+--+  +--+--+--+  +--+  +--+--+  +  +  +  +--+
|x |  |x |x |x |  |     |x    |x |x |x |  |
+--+--+--+--+--+--+     +--+--+--+--+--+--+
levels 1, 3, 4, 5        levels 2, 6


+--+--+--+--+--+     +--+--+--+--+--+
|  |x |x |x |  |     |x    |x |x    |
+  +--+--+--+  +--+  +--+--+  +--+--+--+
|                 |  |  |  |  |  |  |  |
+--+--+--+--+--+--+  +  +  +--+  +  +  +
|x |x |  |x |x |x |  |x |x |  |x |x |x |
+--+--+  +--+--+--+  +--+--+  +--+--+--+
levels 1, 3, 4, 5     levels 2, 6


+--+--+     +--+--+  +--+--+     +--+--+
|  |x |     |  |x |  |   x |     |   x |
+  +--+--+--+  +--+  +--+--+--+--+--+--+
|                 |  |  |  |  |  |  |  |
+--+--+--+--+--+--+  +  +  +  +  +  +  +
|x |x |x |x |x |x |  |x |x |x |x |x |x |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
levels 1, 3, 4, 5     levels 2, 6


+--+--+                 +--+--+
|x |x |                 |x |x |
+--+--+--+--+--+--+--+  +  +  +--+--+--+--+--+
|                 |x |  |  |  |  |  |  |   x |
+--+  +--+--+--+  +--+  +--+--+  +  +  +--+--+
|x |  |x |x |x |  |x |  |x    |x |x |x |   x |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
levels 1, 3, 4, 5        levels 2, 6


   +--+--+                 +--+--+
   |x |x |                 |x |x |
+--+--+--+--+--+--+--+  +--+  +  +--+--+--+--+
|                 |x |  |  |  |  |  |  |   x |
+--+  +--+--+--+  +--+  +  +--+--+  +  +--+--+
|x |  |x |x |x |  |x |  |x |   x |x |x |   x |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
levels 1, 3, 4, 5        levels 2, 6


6x6x8
+--+--+--+--+--+--+--+--+
|                    |  |
+                 +--+  +
|                 |     |
+                 +--+  +
|                    |  |
+                    +  +
|                    |  |
+                    +  +
|                    |  |
+                 +--+  +
|                 |     |
+--+--+--+--+--+--+--+--+
(6 levels deep)


6x8x8  by Robert Reid
+--+--+--+--+--+--+--+--+
|                 |     |
+  +--+--+--+  +--+--+  +
|  |        |  |     |  |
+--+        +--+     +  +
|  |                 |  |
+  +--+              +  +
|     |              |  |
+  +--+--+--+--+--+--+  +
|  |              |     |
+  +              +--+  +
|  |                 |  |
+  +     +--+        +--+
|  |     |  |        |  |
+  +--+--+  +--+--+--+  +
|     |                 |
+--+--+--+--+--+--+--+--+
(6 levels deep)


6x10x16
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                 |                    |        |
+                 +                    +        +
|                 |                    |        |
+     +--+--+     +--+--+--+--+     +--+--+     +
|     |     |     |     |     |     |     |     |
+--+--+     +--+--+     +     +--+--+     +     +
|     |                 |                 |     |
+     +                 +                 +     +
|     |                 |                 |     |
+     +--+--+--+--+--+--+--+--+--+--+--+--+     +
|     |                 |                 |     |
+     +                 +                 +     +
|     |                 |                 |     |
+     +     +--+--+     +     +--+--+     +--+--+
|     |     |     |     |     |     |     |     |
+     +--+--+     +--+--+--+--+     +--+--+     +
|        |                    |                 |
+        +                    +                 +
|        |                    |                 |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
(6 levels deep)

...............................................................................

22*
***


+--+--+        +--+--+        +--+--+        +--+--+
|u  u |        | d ud|        |u | d|        | d   |
+--+  +        +--+  +        +  +  +        +     +
|u |u |        | d|ud|        |u | d|        | d   |
+  +--+--+--+  +  +--+--+--+  +--+--+--+--+  +     +--+--+
|u |        |  | d   |u  u |  |     |ud ud|  |     | d  d|
+  +        +  +     +--+--+  +     +--+  +  +--+--+--+  +
|u |   u  u |  | d   | d  d|  |u  u  u |u |  | d  d  d| d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4


4x4x6 minimal by Patrick Hamlyn
+--+--+--+--+--+--+
|     |           |
+     +           +
|     |           |
+     +--+--+     +
|           |     |
+           +     +
|           |     |
+--+--+--+--+--+--+
(4 levels deep)


same octacube, allowing reflections


2x3x4 minimal by Andrew Clarke
+--+--+--+--+  +--+--+--+--+
|u |u  u  u |  | d| d  d  d|
+  +--+     +  +  +--+--+--+
|u    |     |  | d|        |
+     +--+--+  +  +        +
|u    |u  u |  | d|    d  d|
+--+--+--+--+  +--+--+--+--+
level 1         level 2

...............................................................................

2  2
****


2x4x4 minimal
+--+--+--+--+  +--+--+--+--+
|   u |u    |  |  | d| d|  |
+--+--+--+--+  +  +  +  +  +
|u        u |  | d|  |  | d|
+--+--+--+--+  +--+  +  +--+
|u        u |  | d|  |  | d|
+--+--+--+--+  +  +  +  +  +
|   u |u    |  |  | d| d|  |
+--+--+--+--+  +--+--+--+--+
level 1         level 2


4x4x4 which can be physically assembled in 3d
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|u    |   u |  | d|u    | d|  |u | d|u |u |  | d|    d| d|
+--+  +  +--+  +--+--+--+--+  +--+  +  +--+  +  +--+--+  +
|  |  |  |  |  |u        u |  | d|  |  | d|  |           |
+  +  +  +  +  +--+--+--+--+  +  +  +  +  +  +--+--+--+--+
|u |  |  |u |  | d        d|  |  |  |  |  |  |           |
+--+  +  +--+  +--+--+--+--+  +--+  +  +--+  +  +--+--+  +
|u    |   u |  | d|u    | d|  |u | d|u |u |  | d|    d| d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4

also: 4x4x5, 4x4x6, 4x4x7 which are physically constructible

...............................................................................

**2
**
**


4x8x11 minimal
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|   u  u |  |        |u |  |u |ud ud|     |u  u |ud|  |ud| d  d|     |ud ud| d|  | d|        |  | d  d   |
+  +--+--+  +        +  +  +  +--+--+     +--+--+  +  +  +--+--+     +--+--+  +  +  +        +  +--+--+  +
|  |u  u    |        |u |  |u |ud ud|     |u  u |ud|  |ud| d  d|     |ud ud| d|  | d|        |    d  d|  |
+--+--+--+--+--+--+  +--+  +  +--+--+     +--+--+--+  +--+--+--+     +--+--+  +  +--+  +--+--+--+--+--+--+
|      u |     |u |u |u |  |     | d|       d| d| d|  |u |u |u       |u |     |  | d| d| d|     | d      |
+     +--+--+  +--+--+--+  +--+--+--+--+--+--+--+  +  +  +--+--+--+--+--+--+--+  +--+--+--+  +--+--+     +
|     |     |u |        |  |        |u |ud|        |  |        |ud| d|        |  |        | d|     |     |
+     +     +  +        +  +        +  +  +        +  +        +  +  +        +  +        +  +     +     +
|     |     |u |        |  |        |u |ud|        |  |        |ud| d|        |  |        | d|     |     |
+--+--+     +--+--+--+  +  +  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +  +  +--+--+--+     +--+--+
|u |u       |      u |u |  | d| d|u |     |u | d| d|  |u |u | d|     | d|u |u |  | d| d      |       d| d|
+--+--+--+--+     +--+--+  +--+--+--+--+  +  +--+--+  +--+--+  +  +--+--+--+--+  +--+--+     +--+--+--+--+
|        |u |     |     |  |        |ud|u |        |  |        | d|ud|        |  |     |     | d|        |
+        +  +     +     +  +        +  +  +        +  +        +  +  +        +  +     +     +  +        +
|        |u |     |     |  |        |ud|u |        |  |        | d|ud|        |  |     |     | d|        |
+--+--+  +--+--+--+     +  +  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +  +     +--+--+--+  +--+--+
|u |u |u |u    |u       |  | d| d| d|ud|u | d|     |  |     |u | d|ud|u |u |u |  |       d|    d| d| d| d|
+--+  +--+--+--+--+--+--+  +--+--+--+  +  +--+--+  +  +  +--+--+  +  +--+--+--+  +--+--+--+--+--+--+  +--+
|u |        |   u  u |  |  |ud|u  u |u |u |ud ud|u |  | d|ud ud| d| d| d  d|ud|  |  | d  d   |        | d|
+  +        +  +--+--+  +  +  +--+--+  +  +--+--+  +  +  +--+--+  +  +--+--+  +  +  +--+--+  +        +  +
|u |        |  |u  u    |  |ud|u  u |u |u |ud ud|u |  | d|ud ud| d| d| d  d|ud|  |    d  d|  |        | d|
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 1                     level 2                    level 3                    level 4


same octacube, allowing reflections


3x4x8 co-minimal
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|u |u  u |u |u |u  u    |  | d|ud ud|ud| d|ud ud|u |  |    d  d| d   | d  d| d|
+  +--+--+  +  +--+--+  +  +--+--+--+  +--+--+--+  +  +  +--+--+--+--+--+--+--+
|        |u |        |  |  |        | d|u |        |  |  |        | d|        |
+        +  +        +--+  +        +  +  +        +  +--+        +  +        +
|        |u |        |  |  |        | d|u |        |  |  |        | d|        |
+--+--+--+--+--+--+--+  +  +  +--+--+--+  +--+--+--+  +  +--+--+  +  +--+--+  +
|u |u  u |   u |u  u    |  | d|ud ud|u |ud|ud ud|u |  |    d  d| d| d| d  d| d|
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 1                     level 2                    level 3


4x4x6 co-minimal
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|      u |u |  |u    | d|ud|  |ud|u |    d|  | d| d      |
+     +--+  +  +--+--+--+  +  +  +--+--+--+  +  +--+     +
|     |u |u |  |   u |ud| d|  |u |ud| d   |  | d| d|     |
+     +  +  +  +--+--+  +  +  +  +  +--+--+  +  +  +     +
|     |u |u |  |     | d| d|  |u |u |     |  | d| d|     |
+--+--+  +--+  +     +  +--+  +--+  +     +  +--+  +--+--+
|     |u |u |  |     | d| d|  |u |u |     |  | d| d|     |
+     +--+  +  +     +--+  +  +  +--+     +  +  +--+     +
|     |u |u |  |       d| d|  |u |u       |  | d| d|     |
+     +--+  +  +--+--+--+  +  +  +--+--+--+  +  +--+     +
|      u |u |  |u    | d|ud|  |ud|u |    d|  | d| d      |
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4

also: 3x4x12


...............................................................................
Nonacubes
...............................................................................


****
*
****


+--+--+--+--+--+--+--+--+--+--+--+
|  |         x |  |           |x |
+  +--+--+--+--+  +  +--+--+--+--+
|  |              |  |
+  +--+--+--+--+  +  +--+--+--+--+
|  |         x |  |           |x |
+  +--+--+--+--+  +--+--+--+--+--+
|x |              |x |
+--+              +--+
levels 1, 3        level 2


3x4x6 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+
|              |  |
+  +--+--+--+--+  +
|  |              |
+  +--+--+--+--+  +
|              |  |
+  +--+--+--+--+  +
|  |              |
+--+--+--+--+--+--+
(3 levels deep)

also: 4x5x9

...............................................................................

*
*
*******


3x7x9 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|u |        |        |  | d                  |
+--+  +--+--+--+--+  +  +--+--+--+--+--+--+--+
|u |  |  |        |  |  | d                  |
+--+  +  +--+--+  +  +  +--+--+--+--+--+--+--+
|u |  |  |  |  |  |  |  | d                  |
+--+  +  +  +  +  +  +  +--+--+--+--+--+--+--+
|u |  |  |  |  |  |  |  | d                  |
+--+  +  +  +  +  +  +  +--+--+--+--+--+--+--+
|u |  |  |  |  |  |  |  | d                  |
+--+  +  +  +  +  +  +  +--+--+--+--+--+--+--+
|u |  |  |  |  |  |  |  | d                  |
+--+  +  +  +  +  +  +  +--+--+--+--+--+--+--+
|u |  |  |  |  |  |  |  | d                  |
+--+--+  +  +  +  +--+  +--+--+--+--+--+--+--+
|        |  |  |  |u |  |                   d|
+--+--+--+  +  +--+--+  +--+--+--+--+--+--+--+
|u |        |        |  | d                  |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
levels 1, 2              level 3

...............................................................................

 ***
******


   +--+--+--+           +--+--+--+
   |x |x |x |           |x |x |x |
   +--+--+--+           +  +  +  +
   |        |           |  |  |  |
+--+        +--+--+  +--+--+--+--+--+--+
|                 |  |  |  |  |  |  |  |
+--+--+--+--+--+--+  +  +  +  +  +  +  +
|x |x |x |x |x |x |  |x |x |x |x |x |x |
+--+--+--+--+--+--+  +--+--+--+--+--+--+
levels 1, 5, 6        levels 2, 3, 4


6x6x9
+--+--+--+--+--+--+--+--+--+
|  |                 |     |
+  +--+        +--+--+     +
|     |        |           |
+     +--+--+--+           +
|     |        |           |
+     +        +           +
|     |        |           |
+  +--+        +--+--+     +
|  |                 |     |
+  +                 +     +
|  |                 |     |
+--+--+--+--+--+--+--+--+--+
(6 levels deep)

...............................................................................

** **
*****


      +--+              +--+
      |u |              | d|
      +  +              +  +
      |u |              | d|
+--+--+--+--+--+  +--+--+  +--+--+
|u  u     u  u |  | d  d|  | d  d|
+--+--+--+--+--+  +--+--+  +--+--+
      |u |              | d|
      +  +              +  +
      |u |              | d|
      +--+              +--+
level 1            level 2


+--+--+--+--+        +--+--+--+--+
|x    |   x |        |x |     |x |
+--+--+--+--+        +--+     +--+
|x    |   x |        |x |     |x |
+--+--+--+--+        +--+  +--+--+
|x    |              |x |  |
+--+--+--+--+        +--+  +--+--+
|x    |   x |        |x |     |x |
+--+--+--+--+        +--+     +--+
|x    |   x |        |x |     |x |
+--+--+--+--+        +--+--+--+--+
levels 1, 2, 4, 5     level 3


5x9x10
+--+--+--+--+--+--+--+--+--+
|           |  |           |
+           +  +           +
|           |  |           |
+     +--+--+  +--+--+     +
|     |              |     |
+     +--+--+  +--+--+     +
|           |  |           |
+           +  +           +
|           |  |           |
+--+--+--+--+--+--+--+--+--+
(10 levels deep)

...............................................................................

*** *
*****


+--+--+--+--+--+           +--+--+--+--+--+
|x |x |x |x |x |           |x |x |x |x |x |
+  +  +  +  +  +  +--+     +--+--+--+--+--+  +--+
|  |  |  |  |  |  |x |     |              |  |x |
+--+--+--+--+--+--+  +--+  +        +--+  +--+--+--+
|  |  |  |        |  |  |  |        |  |  |        |
+  +  +  +        +--+  +  +--+--+--+  +--+        +
|x |x |x |              |  |x |x |x |              |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
levels 1, 2, 3, 5           level 4


+--+--+--+           +--+--+--+
|x |x |x |           |x |x |x |
+  +  +  +--+--+     +--+--+--+--+--+
|  |  |  |x    |     |        |x |  |
+--+--+--+--+--+     +        +--+  +
|  |  |  |  |  |     |              |
+  +  +  +  +  +     +--+--+--+--+--+
|x |x |x |x |x |     |x |x |x |x |x |
+--+--+--+--+--+     +--+--+--+--+--+
levels 1, 2, 3, 5     level 4


+--+--+--+           +--+--+--+
|x |x |x |           |x |x |x |
+  +  +  +--+--+--+  +--+--+--+--+--+--+
|  |  |  |x |   x |  |        |x |  |x |
+--+--+--+  +--+--+  +        +--+  +--+
|  |  |  |  |   x |  |              |x |
+  +  +  +--+--+--+  +--+--+--+--+--+--+
|x |x |x |           |x |x |x |
+--+--+--+           +--+--+--+
levels 1, 2, 3, 5     level 4


4x5x18
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|              |              |                       |
+              +  +--+        +                       +
|              |  |  |        |                       |
+              +--+  +--+--+--+--+  +--+              +
|                       |        |  |  |              |
+                       +        +--+  +              +
|                       |              |              |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
(5 levels deep)


5x9x10
+--+--+--+--+--+--+--+--+--+--+
|           |     |           |
+           +     +           +
|           |     |           |
+           +     +           +
|           |     |           |
+        +--+     +--+        +
|        |           |        |
+        +           +        +
|        |           |        |
+--+--+--+           +--+--+--+
|        |           |        |
+        +--+--+--+--+        +
|              |              |
+              +              +
|              |              |
+              +              +
|              |              |
+--+--+--+--+--+--+--+--+--+--+
(5 levels deep)

...............................................................................

*    *
*******


+--+--+--+--+--+--+--+     +--+--+--+--+--+--+--+
|x |  |x    |x    |  |     |x |  |x |  |x |  |  |
+  +  +--+--+--+--+  +--+  +--+  +--+  +--+  +  +--+
|  |                    |  |     |     |     |     |
+--+--+--+--+--+--+--+--+  +--+  +--+  +--+  +  +--+
|x    |x    |x    |x    |  |x |  |x |  |x |  |  |x |
+--+--+--+--+--+--+--+--+  +--+  +--+  +--+  +  +--+
|x    |x    |x    |x    |  |x |  |x |  |x |  |  |x |
+--+--+--+--+--+--+--+--+  +--+  +--+  +--+  +  +--+
|x    |x    |x    |x    |  |x |  |x |  |x |  |  |x |
+--+--+--+--+--+--+--+--+  +--+  +--+  +--+  +  +--+
|x |  |x    |x    |  |     |x |  |x |  |x |  |  |
+  +  +--+--+--+--+  +--+  +--+  +--+  +--+  +  +--+
|  |                    |  |     |     |     |     |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
levels 1, 6                 levels 2, 3, 4, 5, 7


+--+--+                    +--+--+
|x |x |                    |x |x |
+  +  +--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|  |  |  |  |  |  |   x |  |                    |x |
+--+--+  +  +  +  +--+--+  +--+  +--+--+--+--+  +--+
|x    |x |x |x |x |   x |  |x |  |x |x |x |x |  |x |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
levels 1, 6                 levels 2, 3, 4, 5, 7


      +--+--+     +--+--+        +--+--+     +--+--+
      |   x |     |x    |        |  |x |     |x |  |
+--+--+--+--+--+--+--+--+  +--+--+  +--+--+--+--+  +
|x    |  |  |  |  |  |  |  |x |                    |
+--+--+  +  +  +  +  +  +  +--+--+--+--+--+--+--+--+
      |x |x |x |x |x |x |        |x |x |x |x |x |x |
      +--+--+--+--+--+--+        +--+--+--+--+--+--+
levels 1, 6                 levels 2, 3, 4, 5, 7


7x7x9
+--+--+--+--+--+--+--+--+--+
|                    |     |
+                    +--+  +
|                       |  |
+                       +  +
|                       |  |
+                       +  +
|                       |  |
+                       +  +
|                       |  |
+                    +--+  +
|                    |     |
+                    +--+  +
|                       |  |
+--+--+--+--+--+--+--+--+--+
(7 levels deep)


7x8x9
+--+--+--+--+--+--+--+--+--+
|        |  |        |     |
+        +  +        +     +
|        |  |        |     |
+     +--+  +--+     +     +
|     |        |     |     |
+     +        +     +     +
|     |        |     |     |
+     +     +--+     +     +
|     |     |        |     |
+     +     +        +     +
|     |     |        |     |
+     +     +--+  +--+     +
|     |        |  |        |
+     +        +  +        +
|     |        |  |        |
+--+--+--+--+--+--+--+--+--+
(7 levels deep)

...............................................................................

 **
*******


+--+--+--+--+              +--+--+--+--+
|x |     |x |              |x    |   x |
+--+     +--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|                    |x |  |  |  |  |  |  |  |   x |
+--+--+--+--+--+--+--+--+  +  +  +  +  +  +  +--+--+
|x |x |x |x |x |x |        |x |x |x |x |x |x |
+--+--+--+--+--+--+        +--+--+--+--+--+--+
levels 1, 4, 5, 6, 7        levels 2, 3


+--+--+--+--+           +--+--+--+--+
|x |     |x |           |x    |   x |
+--+     +--+--+--+--+  +--+--+--+--+--+--+--+
|                    |  |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +  +  +  +  +
|x |x |x |x |x |x |x |  |x |x |x |x |x |x |x |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
levels 1, 4, 5, 6, 7     levels 2, 3


            +--+--+                 +--+--+
            |x |x |                 |x |x |
+--+--+--+--+--+--+     +--+--+--+--+  +  +
|x |x |x |x |     |     |x |x |x |x |  |  |
+--+--+--+--+     +--+  +  +  +  +  +--+--+--+
|                    |  |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+  +--+--+--+--+  +  +  +
            |x |x |x |              |x |x |x |
            +--+--+--+              +--+--+--+
levels 1, 4, 5, 6, 7     levels 2, 3


3x7x24
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|           |                    |                    |                 |
+           +--+--+--+--+     +--+--+     +--+--+--+--+                 +
|                       |     |     |     |     |                       |
+                 +--+--+--+--+     +--+--+     +--+--+--+--+           +
|                 |                    |                    |           |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
(7 levels deep)


7x12x12
+--+--+--+--+--+--+--+--+--+--+--+--+
|        |     |                    |
+        +     +                    +
|        |     |                    |
+        +     +--+--+--+           +
|        |     |        |           |
+        +     +        +--+--+--+--+
|        |     |                    |
+     +--+     +--+                 +
|     |           |                 |
+     +           +     +--+--+--+--+
|     |           |     |     |     |
+     +     +--+--+--+--+     +     +
|     |     |     |           |     |
+--+--+--+--+     +           +     +
|                 |           |     |
+                 +--+     +--+     +
|                    |     |        |
+--+--+--+--+        +     +        +
|           |        |     |        |
+           +--+--+--+     +        +
|                    |     |        |
+                    +     +        +
|                    |     |        |
+--+--+--+--+--+--+--+--+--+--+--+--+
(7 levels deep)

also: 7x12x15, 7x12x18, 7x12x21

...............................................................................

*   *
*******


+--+--+  +--+--+--+        +--+--+  +--+--+--+
|  |x |  |x |  |x |        |   x |  |x    |x |
+  +--+--+--+  +--+--+--+  +--+--+--+--+--+  +--+--+
|                    |x |  |  |  |  |  |  |  |   x |
+--+--+--+--+--+--+--+--+  +  +  +  +  +  +--+--+--+
|x |x |x |x |x |           |x |x |x |x |x |
+--+--+--+--+--+           +--+--+--+--+--+
levels 1, 2, 4, 5, 6        levels 3, 7


               +--+--+                    +--+--+
               |x |x |                    |x |x |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+  +  +--+
|x |                    |  |x    |  |  |  |  |  |  |
+--+  +--+--+--+  +--+--+  +--+--+  +  +  +--+--+  +
|x |  |x |x |x |  |x |x |  |x    |x |x |x |   x |x |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
levels 1, 2, 4, 5, 6        levels 3, 7


   +--+--+                       +--+--+
   |  |x |                       |   x |
+--+  +--+                    +--+--+--+
|x |  |x |                    |x |   x |
+--+  +--+                    +  +--+--+
|     |x |                    |  |   x |
+--+  +--+                    +--+--+--+
|x |  |                       |x    |
+--+  +--+                    +--+--+--+
   |  |x |                       |   x |
+--+  +--+        +--+--+--+  +--+--+--+        +--+--+--+
|x |  |  |        |  |x |x |  |x    |  |        |  |x |x |
+--+  +  +--+--+--+  +--+--+  +--+--+  +--+--+--+  +  +  +
|     |                    |  |                    |  |  |
+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+
levels 1, 2, 4, 5, 6           levels 3, 7


+--+--+     +--+--+     +--+--+     +--+--+
|  |x |     |  |x |     |   x |     |   x |
+  +--+--+--+  +--+--+  +--+--+--+--+--+--+--+
|                    |  |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +  +  +  +  +
|x |x |x |x |x |x |x |  |x |x |x |x |x |x |x |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
levels 1, 2, 4, 5, 6     levels 3, 7


                  +--+                    +--+
                  |x |                    |x |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+  +
|x |x |  |x |x |x |  |  |x |x |   x |x |x |  |
+--+--+  +--+--+--+  +  +  +  +--+--+  +  +--+
|                    |  |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+  +--+--+  +  +--+--+  +
      |x |x |     |x |        |x |x |     |x |
      +--+--+     +--+        +--+--+     +--+
levels 1, 2, 4, 5, 6     levels 3, 7


6x7x15
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                    |                       |
+--+--+  +--+--+--+  +                       +
|     |  |        |  |                       |
+     +--+        +--+--+     +--+--+--+--+--+
|                       |     |              |
+              +--+--+--+--+--+              +
|              |     |                       |
+--+--+--+--+--+     +--+--+        +--+     +
|                       |  |        |  |     |
+                       +  +--+--+--+  +--+--+
|                       |                    |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
(7 levels deep)


7x9x10
+--+--+--+--+--+--+--+--+--+--+
|                          |  |
+        +--+--+--+        +  +
|        |     |  |        |  |
+--+--+--+--+  +  +     +--+  +
|     |     |  |  |     |     |
+  +--+     +  +  +--+  +--+  +
|  |        |  |     |     |  |
+  +        +  +  +--+     +  +
|  |        |  |  |        |  |
+  +     +--+  +  +        +  +
|  |     |     |  |        |  |
+  +--+  +--+  +  +     +--+  +
|     |     |  |  |     |     |
+  +--+     +  +  +--+--+--+--+
|  |        |  |     |        |
+  +        +--+--+--+        +
|  |                          |
+--+--+--+--+--+--+--+--+--+--+
(7 levels deep)


7x12x12
+--+--+--+--+--+--+--+--+--+--+--+--+
|        |     |                    |
+        +     +                    +
|        |     |                    |
+     +--+     +--+     +--+--+     +
|     |        |  |     |     |     |
+     +        +  +--+--+     +--+--+
|     |        |                    |
+     +--+     +                    +
|        |     |                    |
+        +     +  +--+--+--+--+--+--+
|        |     |  |           |     |
+     +--+     +--+--+     +--+     +
|     |           |  |     |        |
+--+--+--+--+--+--+  +     +        +
|                    |     |        |
+                    +     +--+     +
|                    |        |     |
+--+--+     +--+--+  +        +     +
|     |     |     |  |        |     |
+     +--+--+     +--+     +--+     +
|                    |     |        |
+                    +     +        +
|                    |     |        |
+--+--+--+--+--+--+--+--+--+--+--+--+
(7 levels deep)

...............................................................................

22*
22


4x6x6 minimal
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u  u |u  u |u  u |  | d  d|ud  d| d  d|  |u  u | d|  |u  u |  | d  d   |    d  d|
+     +     +     +  +     +     +     +  +     +--+  +     +  +     +--+--+     +
|u  u |u  u |u  u |  | d  d| d  d| d  d|  |u  u |u  u |u  u |  | d  d| d  d| d  d|
+  +--+--+--+--+  +  +--+--+--+--+--+--+  +--+--+     +--+--+  +--+--+     +--+--+
|  |u  u |u  u |  |  |u | d  d| d  d   |  |ud u |u  u |u  u |  | d  d| d  d| d  d|
+--+     +     +--+  +--+     +     +--+  +     +--+--+     +  +     +--+--+     +
|  |u  u |u  u |  |  |    d  d| d  d|u |  |u  u |u  u |u  ud|  | d  d| d  d| d  d|
+  +--+--+--+--+  +  +--+--+--+--+--+--+  +--+--+     +--+--+  +--+--+     +--+--+
|u  u |u  u |u  u |  | d  d| d  d| d  d|  |u  u |u  u |u  u |  | d  d| d  d| d  d|
+     +     +     +  +     +     +     +  +     +  +--+     +  +     +--+--+     +
|u  u |u  u |u  u |  | d  d| d ud| d  d|  |u  u |  | d|u  u |  | d  d   |    d  d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4

...............................................................................

*2**
****

allowing reflections


3x4x6 minimal
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|           |  |u  u  u  u |  | d  d  d  d|
+           +  +--+--+  +--+  +--+--+--+--+
|   u       |  |u | d|  |u |  | d|     | d|
+--+--+--+--+  +  +--+--+  +  +  +     +  +
|           |  |u |u |   u |  | d| d   | d|
+           +  +  +--+--+  +  +  +     +  +
|      u    |  |u    | d|u |  | d|     | d|
+--+--+--+--+  +  +--+--+  +  +  +     +  +
|      u    |  |u |  | d|u |  | d|     | d|
+           +  +--+  +--+--+  +--+--+--+--+
|           |  |u  u  u  u |  | d  d  d  d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3

...............................................................................

 *  *
*******


      +--+--+  +--+           +--+--+  +--+
      |x |x |  |x |           |x |x |  |x |
+--+--+--+--+--+--+--+  +--+--+  +  +--+  +--+
|                    |  |  |  |  |  |  |  |  |
+--+--+  +--+--+  +--+  +  +  +--+--+  +--+  +
|x |x |  |x |x |  |x |  |x |x |   x |x |  |x |
+--+--+--+--+--+--+--+  +--+--+--+--+--+  +--+
               |x |                    |x |
               +--+                    +--+
levels 1, 2, 4, 5, 7     levels 3, 6


   +--+--+--+--+           +--+--+--+--+
   |  |x |x |  |           |   x |x    |
+--+  +--+--+  +--+--+  +--+--+--+--+--+--+--+
|                    |  |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +  +  +  +  +
|x |x |x |x |x |x |x |  |x |x |x |x |x |x |x |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
levels 1, 2, 4, 5, 7     levels 3, 6


7x7x9
+--+--+--+--+--+--+--+--+--+
|  |                    |  |
+  +--+  +--+--+  +--+--+  +
|     |  |     |  |  |     |
+  +--+--+     +--+  +--+  +
|  |                    |  |
+  +                    +  +
|  |                    |  |
+  +--+--+--+--+--+  +--+  +
|     |           |  |     |
+  +--+           +--+--+  +
|  |                    |  |
+  +                    +  +
|  |                    |  |
+--+--+--+--+--+--+--+--+--+
(7 levels deep)

also: 4x7x27

...............................................................................

*  *
*******


+--+--+  +--+--+  +--+  +--+--+  +--+--+  +--+
|   x |  |   x |  |x |  |  |x |  |  |x |  |x |
+--+--+--+--+--+--+  +  +  +--+--+  +--+--+--+
|  |  |  |  |  |  |  |  |                    |
+  +  +  +  +  +  +--+  +--+--+--+--+--+--+--+
|x |x |x |x |x |x |     |x |x |x |x |x |x |
+--+--+--+--+--+--+     +--+--+--+--+--+--+
levels 1, 2, 3, 5, 6     levels 4, 7


7x8x9
+--+--+--+--+--+--+--+--+--+
|                    |     |
+--+--+--+  +--+--+  +--+  +
|  |     |  |     |  |  |  |
+  +     +--+     +--+  +  +
|  |                    |  |
+  +                 +--+  +
|  |                 |     |
+  +--+--+--+--+--+--+--+  +
|     |                 |  |
+  +--+                 +  +
|  |                    |  |
+  +  +--+     +--+     +  +
|  |  |  |     |  |     |  |
+  +--+  +--+--+  +--+--+--+
|     |                    |
+--+--+--+--+--+--+--+--+--+
(7 levels deep)

also: 4x7x27, 6x7x18


...............................................................................

 *   *
*******


   +--+                    +--+
   |x |                    |x |
   +--+--+  +--+--+--+     +  +--+  +--+--+--+
   |  |x |  |x |  |x |     |  |x |  |x    |x |
+--+  +--+--+--+  +--+  +--+--+  +--+--+--+  +
|                    |  |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+  +  +  +--+  +  +  +--+
|x |x |  |x |x |x |     |x |x |  |x |x |x |
+--+--+  +--+--+--+     +--+--+  +--+--+--+
levels 1, 3, 4, 5, 7     levels 2, 6


+--+--+        +--+--+  +--+--+        +--+--+
|x |  |        |  |x |  |x    |        |   x |
+--+  +--+--+--+  +--+  +--+--+--+--+--+--+--+
|                    |  |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +  +  +  +  +
|x |x |x |x |x |x |x |  |x |x |x |x |x |x |x |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
levels 1, 3, 4, 5, 7     levels 2, 6


   +--+                    +--+
   |x |                    |x |
+--+--+     +--+--+--+  +--+  +     +--+--+--+
|x |  |     |x |  |x |  |x |  |     |x    |x |
+--+  +--+--+--+  +--+  +  +--+--+--+--+--+  +
|                    |  |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+  +--+  +  +  +  +  +--+
   |x |x |x |x |x |        |x |x |x |x |x |
   +--+--+--+--+--+        +--+--+--+--+--+
levels 1, 3, 4, 5, 7     levels 2, 6


+--+--+     +--+--+     +--+--+     +--+--+
|x |  |     |x |  |     |x    |     |x    |
+--+  +--+--+--+  +--+  +--+--+--+--+--+--+--+
|                    |  |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+  +  +  +  +  +  +  +  +
|x |x |x |x |x |x |x |  |x |x |x |x |x |x |x |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
levels 1, 3, 4, 5, 7     levels 2, 6


7x10x18
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|        |  |                    |                    |
+        +  +--+  +--+--+--+  +--+                    +
|        |     |  |        |  |  |                    |
+     +--+     +--+        +--+  +     +--+--+--+     +
|     |                    |     |     |        |     |
+     +     +--+        +--+     +--+--+        +--+--+
|     |     |  |        |  |                    |     |
+     +--+--+  +--+--+--+  +--+              +--+     +
|        |                    |              |        |
+        +--+--+--+--+--+--+--+--+--+--+--+--+        +
|        |              |                    |        |
+     +--+              +--+  +--+--+--+  +--+--+     +
|     |                    |  |        |  |     |     |
+--+--+        +--+--+     +--+        +--+     +     +
|     |        |     |     |                    |     |
+     +--+--+--+     +  +--+        +--+     +--+     +
|                    |  |  |        |  |     |        |
+                    +--+  +--+--+--+  +--+  +        +
|                    |                    |  |        |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
(7 levels deep)


...............................................................................
Dekacubes
...............................................................................


***
***
***
*


+--+--+--+     +--+--+--+     +--+--+--+
|        |     |u |u |u |     | d| d| d|
+        +--+  +  +  +  +--+  +  +  +  +--+
|        |u |  |u |u |u |ud|  | d| d| d| d|
+        +--+  +  +  +  +  +  +  +  +  +  +
|           |  |u |u |u |u |  | d| d| d| d|
+--+--+--+--+  +--+--+--+  +  +  +  +  +  +
|u  u  u    |  | d  d  d|u |  |  |  |  | d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         levels 2, 3    level 4


+--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |           |u |  | d      |       d|
+--+        +--+--+  +--+--+--+--+--+--+
   |        |           |  |  |  |
   +        +           +  +  +  +
   |        |           |  |  |  |
   +--+--+--+           +  +  +  +
   |u |u |u |           | d| d| d|
   +--+--+--+           +--+--+--+
level 1               levels 2, 3, 4


4x4x10 (confirmed minimal by Patrick Hamlyn)
+--+--+--+--+--+--+--+--+--+--+
|        |                 |  |
+        +--+        +--+--+  +
|           |        |        |
+           +        +        +
|           |        |        |
+           +        +        +
|           |        |        |
+--+--+--+--+--+--+--+--+--+--+
(4 levels deep)

also: 4x7x10

...............................................................................

*
*****
****


4x5x9 minimal
+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+
|  |u |   u  u |u |   u  u |  |  |ud u |ud  d|ud u |ud  d|  |    d  d| d|    d  d| d|  |
+  +--+--+--+--+--+--+--+--+  +  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +
|              |           |  |              |           |  |           |              |
+           +--+           +  +           +--+           +  +           +--+           +
|           |              |  |           |              |  |              |           |
+--+--+--+--+--+--+--+--+  +  +--+--+--+--+--+--+--+--+  +  +  +--+--+--+--+--+--+--+--+
|u  u    |u |u  u    |u |  |  | d ud|u  ud| d ud|u  ud|  |  |  | d| d  d   | d| d  d   |
+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+
level 1                        levels 2, 3, 4                level 5

also 1x30x46 by William Rex Marshall, many others

...............................................................................

**
**
******


+--+--+        +--+--+        +--+--+        +--+--+        +--+--+        +--+--+
|u |u |        |ud|ud|        | d| d|        |u |u |        |ud|ud|        | d| d|
+  +  +        +--+--+        +--+--+        +--+--+        +--+--+        +  +  +
|  |  |        |  |  |        |u |u |        |ud|ud|        | d| d|        |  |  |
+  +  +--+     +  +  +--+     +--+--+--+     +--+--+--+     +  +  +--+     +  +  +--+
|  |  |u |     |  |  |ud|     |       d|     |      u |     |  |  |ud|     |  |  | d|
+--+--+--+     +  +  +--+     +--+--+--+     +--+--+--+     +  +  +--+     +--+--+--+
|      u |     |u |u |ud|     |ud|ud| d|     | d| d|u |     |  |  |ud|     |       d|
+--+--+--+     +--+--+--+     +--+--+--+     +--+--+--+     +--+--+--+     +--+--+--+
levels 1, 2     levels 3, 4    levels 5, 6    levels 7, 8    levels 9, 10   levels 11, 12


4x5x12 co-minimal
+--+--+--+--+--+
|     |        |
+     +        +
|     |        |
+     +--+     +
|        |     |
+        +     +
|        |     |
+--+--+--+--+--+
(12 levels deep)


4x6x10 co-minimal
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|  |  |u |u |u |u |  |u  u | d| d| d| d|  | d  d            |
+  +  +  +  +  +  +  +--+--+  +  +  +  +  +--+--+--+--+--+--+
|  |  |u |u |u |u |  |u  u | d| d| d| d|  | d  d            |
+  +  +  +  +  +  +  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|  |  |  |  |  |  |  |        |  |u  u |  |             d  d|
+  +  +  +  +  +  +  +        +  +--+--+  +--+--+--+--+--+--+
|  |  |  |  |  |  |  |        |  |u  u |  |             d  d|
+  +  +  +  +  +  +  +--+--+  +  +--+--+  +--+--+--+--+--+--+
|u |u |  |  |  |  |  | d| d|  |  |u |u |  |  |  |  |  | d| d|
+  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +
|u |u |  |  |  |  |  | d| d|  |  |u |u |  |  |  |  |  | d| d|
+--+--+--+--+--+--+  +--+--+  +  +--+--+  +  +  +  +  +  +  +
|u  u             |  | d  d|  |        |  |  |  |  |  |  |  |
+--+--+--+--+--+--+  +--+--+  +        +  +  +  +  +  +  +  +
|u  u             |  | d  d|  |        |  |  |  |  |  |  |  |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +  +  +  +  +  +  +
|            u  u |  |u |u |u |u | d  d|  | d| d| d| d|  |  |
+--+--+--+--+--+--+  +  +  +  +  +--+--+  +  +  +  +  +  +  +
|            u  u |  |u |u |u |u | d  d|  | d| d| d| d|  |  |
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               levels 2, 3          level 4


5x6x8 co-minimal
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
|u       |  |  |  |ud|u       |  |  | d|ud|        |  |  | d|        |
+--+--+--+  +  +  +--+--+--+--+  +  +--+--+        +  +  +--+        +
|u       |  |  |  |ud|u       |  |  | d|ud|        |  |  | d|        |
+--+--+--+  +  +  +--+--+--+--+  +  +--+--+--+--+  +  +  +--+--+--+  +
|      u |u |  |  |u |u |ud|ud|  |  |ud|ud| d| d|  |  | d| d      |  |
+--+--+--+--+  +  +--+--+--+--+  +  +--+--+--+--+  +  +--+--+--+--+  +
|u |u       |  |  |ud|ud|u |u |  |  | d| d|ud|ud|  |  |       d| d|  |
+  +--+--+--+  +  +--+--+--+--+  +  +--+--+--+--+  +  +--+--+--+  +  +
|  |u |        |  |u |ud|        |  |ud| d      |  |  | d      |  |  |
+  +--+        +  +--+--+        +  +--+--+--+--+  +  +--+--+--+  +  +
|  |u |        |  |u |ud|        |  |ud| d      |  |  | d      |  |  |
+--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+  +--+--+--+--+--+
levels 1, 2        levels 3, 4       levels 5, 6       levels 7, 8


...............................................................................

  **
****
  **
  **


            +--+--+              +--+--+
            |x |x |              |x |x |
            +  +  +              +  +  +
            |x |x |              |x |x |
+--+--+  +--+--+--+  +--+--+  +--+  +  +
|x |x |  |x |     |  |x |x |  |x |  |  |
+  +  +  +  +     +  +  +  +  +  +  +  +
|x |x |  |x |     |  |x |x |  |x |  |  |
+--+--+--+--+     +  +  +  +--+  +--+--+
|     |           |  |  |  |  |  |  |  |
+     +--+--+     +  +  +  +  +  +  +  +
|           |     |  |  |  |  |  |  |  |
+     +--+--+--+--+  +--+--+  +--+  +  +
|     |x |  |x |x |  |  |  |x |  |x |x |
+     +  +  +  +  +  +  +  +  +  +  +  +
|     |x |  |x |x |  |  |  |x |  |x |x |
+--+--+--+  +--+--+  +  +  +--+  +--+--+
|x |x |              |x |x |
+  +  +              +  +  +
|x |x |              |x |x |
+--+--+              +--+--+
levels 1, 2, 4        level 3


4x6x10 minimal by Patrick Hamlyn
+--+--+--+--+--+--+
|           |     |
+           +     +
|           |     |
+--+--+  +--+     +
|     |  |        |
+     +  +        +
|     |  |        |
+     +--+        +
|                 |
+                 +
|                 |
+        +--+     +
|        |  |     |
+        +  +     +
|        |  |     |
+     +--+  +--+--+
|     |           |
+     +           +
|     |           |
+--+--+--+--+--+--+
(4 levels deep)


+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|x |x |x |x |     |x  x |  |x |x |x |x |      x  x |
+  +  +  +  +     +--+--+  +  +  +  +  +--+--+--+--+
|x |x |x |x |     |x  x |  |x |x |x |x |      x  x |
+--+--+--+--+     +--+--+  +  +  +  +  +--+--+--+--+
|     |           |x  x |  |  |  |  |  |      x  x |
+     +--+--+     +--+--+  +  +  +  +  +--+--+--+--+
|           |     |x  x |  |  |  |  |  |      x  x |
+     +--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|     |                    |  |  |
+     +                    +  +  +
|     |                    |  |  |
+--+--+                    +  +  +
|x |x |                    |x |x |
+  +  +                    +  +  +
|x |x |                    |x |x |
+--+--+                    +--+--+
levels 1, 2, 4              level 3


4x8x10
+--+--+--+--+--+--+--+--+--+--+
|                       |     |
+                       +     +
|                       |     |
+                       +     +
|                       |     |
+                       +     +
|                       |     |
+     +--+--+--+--+--+--+     +
|     |                       |
+     +                       +
|     |                       |
+     +                       +
|     |                       |
+     +                       +
|     |                       |
+--+--+--+--+--+--+--+--+--+--+
(4 levels deep)

also: 1x30x32 by William Rex Marshall
also: 6x6x10, many others

...............................................................................

*  *  *
*******


+--+--+--+--+              +--+--+--+--+
|x |x |x |x |              |x |x |x |x |
+  +  +  +  +--+--+--+--+  +--+--+--+--+--+--+--+--+
|  |  |  |  |  |  |   x |  |                    |x |
+--+--+--+--+  +  +--+--+  +  +--+--+  +--+--+  +--+
|   x |x    |x |x |   x |  |  |x |x |  |x |x |  |x |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
levels 1, 4, 7              levels 2, 3, 5, 6


5x7x8 minimal
+--+--+--+--+--+--+--+--+
|                       |
+                       +
|                       |
+--+--+--+--+           +
|           |           |
+           +--+--+--+--+
|                       |
+                       +
|                       |
+--+--+--+--+--+--+--+--+
7 levels deep

also: 4x7x15

...............................................................................

2**2
****


4x5x6 minimal
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u  u |u  u |u  u |  |ud ud|ud ud|ud ud|  |ud ud|ud ud|ud ud|  | d  d| d  d| d  d|
+--+  +  +--+  +--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+  +  +--+  +--+
|u |  |  |  |  |u |  |ud|u  u  u  u |ud|  |ud| d  d  d  d|ud|  | d|  |  |  |  | d|
+  +--+--+  +--+  +  +  +  +--+--+  +  +  +  +--+--+--+--+  +  +  +--+--+  +--+  +
|u    |u  u |   u |  |ud|  |ud ud|  |ud|  |ud|  |ud ud|  |ud|  | d   | d  d|    d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+  +--+--+  +--+  +--+--+--+--+--+--+
|u    |  |  |   u |  |ud|u  u  u  u |ud|  |ud| d  d  d  d|ud|  | d   |  |  |    d|
+  +--+  +  +--+  +  +  +--+--+--+--+  +  +  +--+--+--+--+  +  +  +--+  +  +--+  +
|u |u  u |u  u |u |  |ud|ud ud|ud ud|ud|  |ud|ud ud|ud ud|ud|  | d| d  d| d  d| d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               level 2              level 3              level 4

...............................................................................

*22*
****


+--+     +--+  +--+     +--+  +--+     +--+  +--+     +--+
|u |     |u |  |ud|     |ud|  |ud|     |ud|  | d|     | d|
+  +--+--+  +  +  +--+--+  +  +  +--+--+  +  +  +--+--+  +
|u |     |u |  |ud u |u  ud|  |ud  d| d ud|  | d|     | d|
+--+     +--+  +--+--+--+--+  +--+--+--+--+  +--+     +--+
|u  u  u  u |  | d  d  d  d|  |u  u  u  u |  | d  d  d  d|
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3        level 4


   +--+--+--+--+        +--+--+--+--+        +--+--+--+--+        +--+--+--+--+
   |u  u |u  u |        |ud ud|ud ud|        |ud ud|ud ud|        | d  d| d  d|
+--+--+--+--+--+--+  +--+  +--+--+  +--+  +--+  +--+--+  +--+  +--+--+--+--+--+--+
|u |   u  u    |u |  |ud|u | d  d|u |ud|  |ud| d|u  u | d|ud|  | d|    d  d   | d|
+  +           +  +  +  +--+--+--+--+  +  +  +--+--+--+--+  +  +  +           +  +
|u |           |u |  |ud u |     |u  ud|  |ud  d|     | d ud|  | d|           | d|
+--+--+--+--+--+--+  +--+--+     +--+--+  +--+--+     +--+--+  +--+--+--+--+--+--+
   |u  u  u  u |        | d  d  d  d|        |u  u  u  u |        | d  d  d  d|
   +--+--+--+--+        +--+--+--+--+        +--+--+--+--+        +--+--+--+--+
level 1               level 2              level 3              level 4


4x4x10 minimal
+--+--+--+--+--+--+--+--+--+--+
|        |           |        |
+     +--+           +--+     +
|     |                 |     |
+     +                 +     +
|     |                 |     |
+     +--+           +--+     +
|        |           |        |
+--+--+--+--+--+--+--+--+--+--+
(4 levels deep)

also: 4x6x10

...............................................................................

2**
2**
2


3x8x10 minimal
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|     |   u |u |u  u  u |  |u  u  u |ud|ud| d  d  d|  | d  d  d| d| d   |     |
+     +     +  +--+--+--+  +--+     +  +  +     +--+  +--+--+--+  +     +     +
|u    |   u |u |     |u |  |ud|     |ud|ud|     |ud|  | d|     | d| d   |    d|
+     +     +--+     +  +  +  +     +--+--+     +  +  +  +     +--+     +     +
|u    |     |u |     |u |  |ud|     |u | d|     |ud|  | d|     | d|     |    d|
+--+--+--+--+  +     +--+  +--+--+--+  +  +--+--+--+  +--+     +  +--+--+--+--+
|     |      u |u  u  u |  |u  u  u |u | d| d  d  d|  | d  d  d| d      |     |
+     +        +--+--+--+  +--+--+--+  +  +--+--+--+  +--+--+--+        +     +
|     |      u |u  u  u |  |u  u  u |u | d| d  d  d|  | d  d  d| d      |     |
+     +--+--+--+--+     +  +--+--+--+--+--+--+--+--+  +     +--+--+--+--+     +
|u  u  u |u       |     |  | d  d  d| d|u |u  u  u |  |     |       d| d  d  d|
+--+--+--+        +     +  +--+--+--+  +  +--+--+--+  +     +        +--+--+--+
|u  u  u |u       |     |  | d  d  d| d|u |u  u  u |  |     |       d| d  d  d|
+--+     +  +--+--+--+--+  +--+--+--+  +  +--+--+--+  +--+--+--+--+  +     +--+
|u |     |u |     |   u |  |ud|     | d|u |     |ud|  | d   |     | d|     | d|
+  +     +--+     +     +  +  +     +--+--+     +  +  +     +     +--+     +  +
|u |     |u |u    |   u |  |ud|     |ud|ud|     |ud|  | d   |    d| d|     | d|
+--+--+--+  +     +     +  +--+     +  +  +     +--+  +     +     +  +--+--+--+
|u  u  u |u |u    |     |  | d  d  d|ud|ud|u  u  u |  |     |    d| d| d  d  d|
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 1                     level 2                    level 3


same dekacube, allowing reflections


+--+--+--+  +--+--+--+  +--+--+--+
|u  u  u |  |      u |  |     | d|
+--+--+  +  +--+--+  +  +     +  +
|u |u |u |  |u |  |u |  | d   | d|
+  +  +--+  +  +  +--+  +     +--+
|u |u |     |u |  |     | d   |
+--+  +     +--+  +     +--+--+
|u  u |     |u  u |     | d  d|
+--+--+     +--+--+     +--+--+
level 1      level 2     level 3


3x4x5 minimal
+--+--+--+--+--+
|        |     |
+        +     +
|        |     |
+     +--+     +
|     |        |
+     +        +
|     |        |
+--+--+--+--+--+
(3 levels deep)


...............................................................................

* * **
******


+--+--+--+--+        +--+--+--+--+
|x    |   x |        |x |     |x |
+--+--+--+--+        +--+  +--+--+
|x    |x |           |x |  |x |
+--+--+  +           +--+  +--+
|x    |  |           |x |     |
+--+--+--+           +--+  +--+
|x    |x |           |x |  |x |
+--+--+  +           +--+  +--+
|x    |  |           |x |     |
+--+--+--+--+        +--+     +--+
|x    |   x |        |x |     |x |
+--+--+--+--+        +--+--+--+--+
levels 1, 3, 5, 6     levels 2, 4


+--+  +--+  +--+        +--+  +--+  +--+
|x |  |x |  |x |        |x |  |x |  |x |
+  +--+  +--+  +--+--+  +--+--+--+--+--+--+--+
|  |x |  |x |  |   x |  |  |x |  |x |     |x |
+--+  +--+  +--+--+--+  +  +--+  +--+     +--+
|  |  |  |  |  |   x |  |                 |x |
+  +--+  +--+  +--+--+  +--+--+--+--+--+--+--+
|x |  |x |  |x |        |x |  |x |  |x |
+--+  +--+  +--+        +--+  +--+  +--+
levels 1, 3, 5, 6        levels 2, 4


6x6x10
+--+--+--+--+--+--+--+--+--+--+
|           |                 |
+        +--+  +--+  +--+     +
|        |  |  |  |  |  |     |
+        +  +--+  +--+  +--+--+
|        |                    |
+        +                    +
|        |                    |
+        +  +--+  +--+  +--+--+
|        |  |  |  |  |  |     |
+        +--+  +--+  +--+     +
|           |                 |
+--+--+--+--+--+--+--+--+--+--+
(6 levels deep)

...............................................................................

* ** *
******


6x8x10
+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+
|x |x    |x    |   x |   x |x |  |x |x |  |x |     |x |  |x |x |
+  +--+--+--+--+--+--+--+--+  +  +--+--+  +--+     +--+  +--+--+
|  |     |     |     |     |  |  |     |                 |     |
+--+  +--+--+  +  +--+--+  +--+  +--+  +--+--+--+--+--+--+  +--+
|x |  |   x |  |  |x    |  |x |  |x |  |  |x |     |x |  |  |x |
+  +  +--+--+  +  +--+--+  +  +  +--+  +  +--+     +--+  +  +--+
|  |     |     |     |     |  |  |     |                 |     |
+--+     +     +     +     +--+  +     +--+--+--+--+--+--+     +
|  |     |     |     |     |  |  |     |                 |     |
+  +  +--+--+  +  +--+--+  +  +  +--+  +  +--+     +--+  +  +--+
|x |  |   x |  |  |x    |  |x |  |x |  |  |x |     |x |  |  |x |
+--+  +--+--+  +  +--+--+  +--+  +--+  +--+--+--+--+--+--+  +--+
|  |     |     |     |     |  |  |     |                 |     |
+  +--+--+--+--+--+--+--+--+  +  +--+--+  +--+     +--+  +--+--+
|x |x    |x    |   x |   x |x |  |x |x |  |x |     |x |  |x |x |
+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+
levels 1, 3, 4, 6                 levels 2, 5


...............................................................................
11-cubes
...............................................................................


***
****
****


4x6x11 minimal by Patrick Hamlyn
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u  u |           |  |ud ud u |        |  | d  d  d|        |
+--+--+           +  +--+--+--+        +  +--+--+--+        +
|     |           |  |u |u |           |  | d| d|           |
+     +--+        +  +  +  +           +  +  +  +           +
|        |        |  |u |u |           |  | d| d|           |
+        +--+--+--+  +  +  +--+--+--+--+  +  +  +--+--+--+--+
|        |        |  |u |u |           |  | d| d|           |
+        +        +  +  +  +           +  +--+--+           +
|        |        |  |  |  |           |  |     |           |
+--+--+--+        +  +--+--+--+        +  +     +--+        +
|        |        |  |        |        |  |        |        |
+        +--+     +  +        +--+--+--+  +        +--+--+--+
|           |     |  |           |  |  |  |        |        |
+           +--+--+  +           +  +  +  +        +        +
|           |u |u |  |           | d| d|  |        |        |
+--+--+--+--+  +  +  +--+--+--+--+  +  +  +--+--+--+        +
|           |u |u |  |           | d| d|  |        |        |
+           +  +  +  +           +  +  +  +        +--+     +
|           |u |u |  |           | d| d|  |           |     |
+        +--+--+--+  +        +--+--+--+  +           +--+--+
|        |u  u  u |  |        | d ud ud|  |           | d  d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               levels 2, 3          level 4


+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |u |u |u  u  u |  |ud|ud|ud|ud ud ud|  |  |  |  | d ud ud|  |           | d  d|
+  +  +  +--+--+--+  +  +  +  +--+--+--+  +  +  +  +--+--+--+  +           +--+--+
|u |u |u |u  u  u |  |ud|ud|ud|ud ud ud|  |  |  |  | d ud ud|  |           | d  d|
+  +  +  +--+--+--+  +  +  +  +--+--+--+  +  +  +  +--+--+--+  +        +--+--+--+
|u |u |u |           |ud|ud|ud|           |  |  |  |           |        |
+  +  +  +           +  +  +  +           +--+--+--+           +--+--+--+
|u |u |u |           | d| d| d|           |u |u |u |           | d| d| d|
+--+--+--+           +--+--+--+           +  +  +  +           +  +  +  +
|        |           |u |u |u |           |ud|ud|ud|           | d| d| d|
+        +           +  +  +  +           +  +  +  +           +  +  +  +
|        |           |u |u |u |           |ud|ud|ud|           | d| d| d|
+        +           +  +  +  +           +  +  +  +           +  +  +  +
|        |           |u |u |u |           |ud|ud|ud|           | d| d| d|
+     +--+           +--+--+--+           +--+--+--+           +--+--+--+
|     |              |u |u |              |ud|ud|              | d| d|
+--+--+              +  +  +              +  +  +              +  +  +
|u |u |              |ud|ud|              |ud|ud|              | d| d|
+  +  +              +  +  +              +  +  +              +  +  +
|u |u |              |ud|ud|              |ud|ud|              | d| d|
+--+--+              +--+--+              +--+--+              +--+--+
level 1               level 2              level 3              level 4


4x10x11
+--+--+--+--+--+--+--+--+--+--+--+
|                 |        |     |
+                 +        +     +
|                 |        |     |
+        +--+--+--+        +     +
|        |        |        |     |
+        +        +     +--+     +
|        |        |     |        |
+        +        +--+--+        +
|        |        |     |        |
+        +     +--+     +        +
|        |     |        |        |
+        +--+--+        +        +
|        |     |        |        |
+     +--+     +        +        +
|     |        |        |        |
+     +        +--+--+--+        +
|     |        |                 |
+     +        +                 +
|     |        |                 |
+--+--+--+--+--+--+--+--+--+--+--+
(4 levels deep)

also: 1x22x25 (by William Rex Marshall and Ingo Wrede, independently)
also: 4x7x22, many others

...............................................................................

***
***
***
*
*


5x6x11 minimal by Patrick Hamlyn
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|        |u  u  u |  |u |       d  d  d|  | d|              |
+        +--+--+--+  +  +--+--+--+--+--+  +  +--+--+        +
|        |        |  |u |u |u |        |  | d| d| d|        |
+        +        +  +  +  +  +        +  +  +  +  +        +
|        |        |  |u |u |u |        |  | d| d| d|        |
+  +--+--+        +  +  +  +  +        +  +--+  +  +--+--+--+
|  |u |u |        |  |  |ud|ud|        |  |  | d| d|        |
+  +--+--+--+--+  +  +  +--+--+--+--+  +  +  +--+--+        +
|  |u |u |u |u |  |  |  |ud|ud| d| d|  |  |  | d| d|        |
+--+  +  +  +  +  +  +--+  +  +  +  +  +  +  +--+--+        +
|  |u |u |u |u |  |  |  | d| d| d| d|  |  |        |        |
+  +  +  +  +  +--+  +  +  +  +  +  +--+  +        +--+--+  +
|  |u |u |u |u |  |  |  | d| d|ud|ud|  |  |        | d| d|  |
+  +--+--+--+--+  +  +  +--+--+--+--+  +  +        +--+--+  +
|        |u |u |  |  |        |ud|ud|  |  |        | d| d|  |
+        +--+--+  +  +        +  +  +  +  +--+--+--+  +  +--+
|        |        |  |        |u |u |u |  |        | d| d| d|
+        +        +  +        +  +  +  +  +        +  +  +  +
|        |        |  |        |u |u |u |  |        | d| d| d|
+--+--+--+        +  +--+--+--+--+--+  +  +        +--+--+  +
|u  u  u |        |  | d  d  d      |u |  |              | d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
levels 1, 2           level 3              levels 4, 5

also: 1x54x55, many others

...............................................................................

*
*****
*****


3x10x11 co-minimal
+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+
|  |u |u |u |u |              |u |  |  | d| d| d| d|  |             d|
+  +--+--+--+--+              +--+  +  +  +  +  +  +  +--+--+--+--+--+
|              |              |u |  |  |  |  |  |  |  |             d|
+              +  +--+--+--+--+--+  +  +  +  +  +  +  +--+--+--+--+--+
|              |  |     |     |u |  |  |  |  |  |  |  |             d|
+--+--+--+--+--+--+     +     +--+  +  +  +  +  +  +  +--+--+--+--+--+
|        |        |     |     |u |  |  |  |  |  |  |  |             d|
+--+     +     +--+     +     +--+  +  +  +  +  +  +  +--+--+--+--+--+
|u |     |     |u |     |     |u |  | d|  |  |  |  | d|             d|
+--+     +     +--+     +     +--+  +--+--+--+--+--+--+--+--+--+--+--+
|u |     |     |u |     |     |u |  | d            | d|  |  |  |  | d|
+--+     +     +--+     +     +--+  +--+--+--+--+--+  +  +  +  +  +  +
|u |     |     |        |        |  | d            |  |  |  |  |  |  |
+--+     +     +--+--+--+--+--+--+  +--+--+--+--+--+  +  +  +  +  +  +
|u |     |     |  |              |  | d            |  |  |  |  |  |  |
+--+--+--+--+--+  +              +  +--+--+--+--+--+  +  +  +  +  +  +
|u |              |              |  | d            |  |  |  |  |  |  |
+--+              +--+--+--+--+  +  +--+--+--+--+--+  +  +  +  +  +  +
|u |              |u |u |u |u |  |  | d            |  | d| d| d| d|  |
+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+
level 1                              levels 2, 3


5x6x11 co-minimal
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |u |u |u |u |  |  | d| d| d| d| d|u |  |  |             d|
+  +  +  +  +  +  +  +--+--+--+--+--+--+  +  +--+--+--+--+--+
|  |  |  |  |  |  |  |              |u |  |  |             d|
+  +  +  +  +  +  +  +              +--+  +  +--+--+--+--+--+
|  |  |  |  |  |  |  |              |u |  |  |             d|
+  +  +  +  +  +  +  +  +--+--+--+--+--+  +  +--+--+--+--+--+
|  |  |  |  |  |  |  |  |     |        |  |  |              |
+  +  +  +  +  +  +  +--+     +     +--+  +  +              +
|  |  |  |  |  |u |  |u |     |     | d|  | d|              |
+--+--+--+--+--+--+  +--+     +     +--+  +--+--+--+--+--+  +
|  |            u |  |u |     |     | d|  | d            |  |
+  +--+--+--+--+--+  +--+     +     +--+  +--+--+--+--+--+--+
|              |u |  |u |     |     | d|  | d|  |  |  |  |  |
+              +  +  +--+     +     +--+  +  +  +  +  +  +  +
|              |  |  |        |     |  |  |  |  |  |  |  |  |
+--+--+--+--+--+  +  +--+--+--+--+--+  +  +  +  +  +  +  +  +
|u             |  |  | d|              |  |  |  |  |  |  |  |
+--+--+--+--+--+  +  +--+              +  +  +  +  +  +  +  +
|u             |  |  | d|              |  |  |  |  |  |  |  |
+--+--+--+--+--+  +  +--+--+--+--+--+--+  +  +  +  +  +  +  +
|u             |  |  | d|u |u |u |u |u |  |  | d| d| d| d| d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
levels 1, 2           level 3              levels 4, 5


...............................................................................
12-cubes
...............................................................................


  **
****
******


3x8x10 minimal
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
|u |u |                 |  | d| d|                 |  |                 |  |  |
+  +  +--+--+           +  +  +  +--+--+           +  +           +--+--+  +  +
|u |u |     |           |  | d| d|     |           |  |           |     |  |  |
+  +  +     +     +--+--+  +  +  +     +     +--+--+  +--+--+     +     +  +  +
|u |u |     |     |u |u |  |ud|ud|     |     |ud|ud|  | d| d|     |     | d| d|
+  +  +     +--+--+  +  +  +  +  +     +--+--+  +  +  +  +  +--+--+     +  +  +
|u |u |        |  |u |u |  |ud|ud|        |  |ud|ud|  | d| d|  |        | d| d|
+  +  +        +  +--+--+  +--+--+        +  +  +  +  +--+--+  +        +  +  +
|  |  |        |  |  |  |  |u |u |        |  |u |u |  | d| d|  |        | d| d|
+  +  +  +--+--+  +  +  +  +  +  +  +--+--+  +  +  +  +  +  +  +--+--+  +  +  +
|  |  |  |        |  |  |  |u |u |  |        |u |u |  | d| d|        |  | d| d|
+--+--+  +        +  +  +  +  +  +  +        +--+--+  +  +  +        +  +--+--+
|u |u |  |        |u |u |  |ud|ud|  |        |ud|ud|  | d| d|        |  | d| d|
+  +  +--+--+     +  +  +  +  +  +--+--+     +  +  +  +  +  +     +--+--+  +  +
|u |u |     |     |u |u |  |ud|ud|     |     |ud|ud|  | d| d|     |     | d| d|
+--+--+     +     +  +  +  +--+--+     +     +  +  +  +  +  +     +     +--+--+
|           |     |u |u |  |           |     | d| d|  |  |  |     |           |
+           +--+--+  +  +  +           +--+--+  +  +  +  +  +--+--+           +
|                 |u |u |  |                 | d| d|  |  |  |                 |
+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+
level 1                     level 2                    level 3

also: 1x45x48, many others

...............................................................................

2222
 **
 **


3x4x4 minimal
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+
|u |u  u |u |  | d|ud ud| d|  |    d  d   |
+  +--+--+  +  +  +--+--+  +  +           +
|u       |u |  | d|       d|  |           |
+        +  +  +  +        +  +--+--+--+--+
|u       |u |  | d|       d|  |           |
+  +--+--+  +  +  +--+--+  +  +           +
|u |u  u |u |  | d|ud ud| d|  |    d  d   |
+--+--+--+--+  +--+--+--+--+  +--+--+--+--+
level 1         level 2        level 3


...............................................................................
13-cubes
...............................................................................


****
****
*****


6x6x13 minimal
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |u |u |u |u |u |  | d| d| d| d| d| d|  |        |        |
+--+--+--+--+--+--+  +  +  +  +  +  +  +  +        +        +
|        |        |  |  |  |  |  |  |  |  |        |        |
+        +        +  +  +  +  +  +  +  +  +        +        +
|        |        |  |  |  |  |  |  |  |  |        |        |
+        +        +  +--+--+--+--+--+--+  +        +        +
|        |        |  |  |  |  |  |  |  |  |        |        |
+        +        +  +  +  +  +  +  +  +  +  +--+--+--+--+  +
|        |        |  |  |  |  |  |  |  |  |  |           |  |
+  +--+--+--+--+  +  +  +  +  +  +  +  +  +--+           +--+
|  |u |u |u |u |  |  |u | d| d| d| d|u |  | d|           | d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+           +--+
|              |u |  |u       |       d|  | d|              |
+--+           +--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
|u |           |u |  | d|u |u |u |u | d|  |  | d| d| d| d|  |
+--+           +--+  +  +  +  +  +  +  +  +  +--+--+--+--+  +
|  |           |  |  |  |  |  |  |  |  |  |        |        |
+  +--+--+--+--+  +  +  +  +  +  +  +  +  +        +        +
|        |        |  |  |  |  |  |  |  |  |        |        |
+        +        +  +--+--+--+--+--+--+  +        +        +
|        |        |  |  |  |  |  |  |  |  |        |        |
+        +        +  +  +  +  +  +  +  +  +        +        +
|        |        |  |  |  |  |  |  |  |  |        |        |
+        +        +  +  +  +  +  +  +  +  +--+--+--+--+--+--+
|        |        |  |u |u |u |u |u |u |  | d| d| d| d| d| d|
+--+--+--+--+--+--+  +--+--+--+--+--+--+  +--+--+--+--+--+--+
level 1               levels 2, 3, 4, 5    level 6


...............................................................................
14-cubes
...............................................................................


  **
  **
*****
*****


+--+--+--+--+     +--+--+--+--+
|x  x |     |     |x  x       |
+--+--+     +     +--+--+--+--+
|x  x |     |     |x  x       |
+--+--+     +--+  +--+--+--+--+--+
|              |  |  |  |  |  |  |
+              +  +  +  +  +  +  +
|              |  |  |  |  |  |  |
+--+--+--+--+--+  +  +  +  +  +  +
|x |x |x |x |x |  |x |x |x |x |x |
+  +  +  +  +  +  +  +  +  +  +  +
|x |x |x |x |x |  |x |x |x |x |x |
+--+--+--+--+--+  +--+--+--+--+--+
levels 1, 2, 5     levels 3, 4


5x6x14 minimal
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|           |              |              |
+           +              +              +
|           |              |              |
+           +--+     +--+--+              +
|              |     |     |              |
+              +     +     +              +
|              |     |     |              |
+              +--+--+     +--+           +
|              |              |           |
+              +              +           +
|              |              |           |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
(5 levels deep)

also: 1x63x80, many others

...............................................................................

******
****
****


4x7x12 minimal by Patrick Hamlyn
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|      u  u  u  u |u |  |u |  | d  d  d  d| d|  | d|        |        |
+--+--+--+--+--+--+  +  +  +  +--+--+--+--+  +  +  +        +        +
|      u  u  u  u |u |  |u |  | d  d  d  d| d|  | d|        |        |
+--+--+--+--+--+--+  +  +  +  +--+--+--+--+  +  +  +        +        +
|  |        |u |u |u |  |u |        | d| d| d|  | d|        |        |
+  +        +  +  +  +  +  +        +  +  +  +  +  +        +        +
|  |        |u |u |u |  |u |        | d| d| d|  | d|        |        |
+  +        +  +  +  +  +--+        +  +  +--+  +  +--+--+  +  +--+--+
|u |        |u |u |  |  | d|        | d| d|u |  |  |  |  |  |  |  | d|
+  +        +  +  +  +  +  +        +  +  +  +  +  +  +  +  +  +  +  +
|u |        |u |u |  |  | d|        | d| d|u |  |  |  |  |  |  |  | d|
+  +  +--+--+  +  +--+  +  +--+--+--+--+--+  +  +--+  +  +--+--+  +  +
|u |  |  |  |  |  |  |  | d|u |u |        |u |  |  | d| d|        | d|
+  +  +  +  +  +  +  +  +  +  +  +        +  +  +  +  +  +        +  +
|u |  |  |  |  |  |  |  | d|u |u |        |u |  |  | d| d|        | d|
+--+--+  +  +--+--+  +  +--+  +  +        +--+  +  +  +  +        +  +
|        |        |u |  |u |u |u |        | d|  | d| d| d|        |  |
+        +        +  +  +  +  +  +        +  +  +  +  +  +        +  +
|        |        |u |  |u |u |u |        | d|  | d| d| d|        |  |
+        +        +  +  +  +--+--+--+--+  +  +  +  +--+--+--+--+--+--+
|        |        |u |  |u |u  u  u  u |  | d|  | d| d  d  d  d      |
+        +        +  +  +  +--+--+--+--+  +  +  +  +--+--+--+--+--+--+
|        |        |u |  |u |u  u  u  u |  | d|  | d| d  d  d  d      |
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
level 1                  levels 2, 3             level 4

also: 1x66x84


...............................................................................
15-cubes
...............................................................................


*
*******
*******


3x7x15 minimal
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
|                  u |  |        |        | d|
+--+--+--+--+--+--+--+  +--+     +     +--+--+
|u                   |  | d|     |     |     |
+--+--+--+--+--+--+--+  +--+     +     +     +
|u                   |  | d|     |     |     |
+--+--+--+--+--+--+--+  +--+     +     +     +
|u                   |  | d|     |     |     |
+--+--+--+--+--+--+--+  +--+     +     +     +
|u                   |  | d|     |     |     |
+--+--+--+--+--+--+--+  +--+     +     +     +
|u                   |  | d|     |     |     |
+--+--+--+--+--+--+--+  +--+     +     +     +
|u                   |  | d|     |     |     |
+--+--+--+--+--+--+--+  +--+--+--+--+--+     +
|u                   |  | d|        |        |
+--+--+--+--+--+--+--+  +--+--+     +--+--+--+
|                  u |  |     |     |     | d|
+--+--+--+--+--+--+--+  +     +     +     +--+
|                  u |  |     |     |     | d|
+--+--+--+--+--+--+--+  +     +     +     +--+
|                  u |  |     |     |     | d|
+--+--+--+--+--+--+--+  +     +     +     +--+
|                  u |  |     |     |     | d|
+--+--+--+--+--+--+--+  +     +     +     +--+
|                  u |  |     |     |     | d|
+--+--+--+--+--+--+--+  +     +     +     +--+
|                  u |  |     |     |     | d|
+--+--+--+--+--+--+--+  +     +--+--+     +--+
|                  u |  |        |        | d|
+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+
levels 1, 2              level 3

also: 1x30x30 by William Rex Marshall


...............................................................................
16-cubes
...............................................................................

* * *  * *
***********


+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+
|x |x |x |x |x |x |x |x |x |x |x |  |x |x |x |x |x |x |x |x |x |x |x |
+--+--+--+--+--+--+--+--+--+--+--+  +  +  +  +  +  +  +  +  +  +  +  +
|                                |  |  |  |  |  |  |  |  |  |  |  |  |
+  +--+  +--+  +--+--+  +--+  +--+  +--+--+--+--+--+--+--+--+--+--+--+
|  |x |  |x |  |x |x |  |x |  |     |   x |   x |   x |x    |x    |
+--+--+--+--+--+--+--+--+--+--+     +--+--+--+--+--+--+--+--+--+--+
levels 1, 3, 5, 6, 8, 10             levels 2, 4, 7, 9, 11


                              +--+                                +--+
                              |x |                                |x |
+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+  +
|x |  |x |  |x |x |  |x |  |x |  |  |x |   x |   x |x    |x    |x |  |
+--+  +--+  +--+--+  +--+  +--+  +  +  +--+--+--+--+--+--+--+--+  +--+
|                                |  |  |  |  |  |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+--+--+--+--+  +--+  +  +  +  +  +  +  +  +--+  +
   |x |x |x |x |x |x |x |x |  |x |     |x |x |x |x |x |x |x |x |  |x |
   +--+--+--+--+--+--+--+--+  +--+     +--+--+--+--+--+--+--+--+  +--+
levels 1, 3, 5, 6, 8, 10             levels 2, 4, 7, 9, 11


+--+                       +--+     +--+                       +--+
|x |                       |x |     |x |                       |x |
+--+--+--+--+--+--+--+--+--+--+--+  +  +--+--+--+--+--+--+--+--+  +--+
|  |x |  |x |  |x |x |  |x |  |x |  |  |x |   x |   x |x    |x |  |x |
+  +--+  +--+  +--+--+  +--+  +--+  +--+  +--+--+--+--+--+--+  +--+  +
|                                |  |  |  |  |  |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+--+--+--+--+  +  +--+  +  +  +  +  +  +--+  +--+
|x |  |x |x |x |x |x |x |  |x |     |x |  |x |x |x |x |x |x |  |x |
+--+  +--+--+--+--+--+--+  +--+     +--+  +--+--+--+--+--+--+  +--+
levels 1, 3, 5, 6, 8, 10             levels 2, 4, 7, 9, 11


   +--+                 +--+  +--+     +--+                 +--+  +--+
   |x |                 |x |  |x |     |x |                 |x |  |x |
+--+--+--+--+--+--+--+--+--+--+--+  +--+  +--+--+--+--+--+--+  +--+  +
|x |  |x |  |x |x |  |x |  |x |  |  |x |  |x |   x |x    |x |  |x |  |
+--+  +--+  +--+--+  +--+  +--+  +  +  +--+  +--+--+--+--+  +--+  +--+
|                                |  |  |  |  |  |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+--+--+--+--+  +--+  +--+  +  +  +  +--+  +--+  +
   |x |  |x |x |x |x |  |x |  |x |     |x |  |x |x |x |x |  |x |  |x |
   +--+  +--+--+--+--+  +--+  +--+     +--+  +--+--+--+--+  +--+  +--+
levels 1, 3, 5, 6, 8, 10             levels 2, 4, 7, 9, 11


+--+  +--+           +--+  +--+     +--+  +--+           +--+  +--+
|x |  |x |           |x |  |x |     |x |  |x |           |x |  |x |
+--+--+--+--+--+--+--+--+--+--+--+  +  +--+  +--+--+--+--+  +--+  +--+
|  |x |  |x |  |x |x |  |x |  |x |  |  |x |  |x |   x |x |  |x |  |x |
+  +--+  +--+  +--+--+  +--+  +--+  +--+  +--+  +--+--+  +--+  +--+  +
|                                |  |  |  |  |  |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+--+--+--+--+  +  +--+  +--+  +  +--+  +--+  +--+
|x |  |x |  |x |x |  |x |  |x |     |x |  |x |  |x |x |  |x |  |x |
+--+  +--+  +--+--+  +--+  +--+     +--+  +--+  +--+--+  +--+  +--+
levels 1, 3, 5, 6, 8, 10             levels 2, 4, 7, 9, 11


11x11x16
+--+--+--+--+--+--+--+--+--+--+--+
|                                |
+                                +
|                                |
+                             +--+
|                             |  |
+--+--+--+--+--+--+--+--+--+--+  +
|                                |
+                                +
|                                |
+--+                       +--+  +
|  |                       |  |  |
+  +--+--+--+--+--+--+--+--+  +--+
|                                |
+                                +
|                                |
+  +--+                 +--+  +--+
|  |  |                 |  |  |  |
+--+  +--+--+--+--+--+--+  +--+  +
|                                |
+                                +
|                                |
+--+  +--+           +--+  +--+  +
|  |  |  |           |  |  |  |  |
+  +--+  +--+--+--+--+  +--+  +--+
|                                |
+                                +
|                                |
+  +--+  +--+     +--+  +--+  +--+
|  |  |  |  |     |  |  |  |  |  |
+--+  +--+  +--+--+  +--+  +--+  +
|                                |
+--+--+--+--+--+--+--+--+--+--+--+
(11 levels deep)


also: 11x12x16

...............................................................................

* *  * * *
***********


      +--+--+     +--+--+--+--+--+--+        +--+--+     +--+--+--+--+--+--+
      |x |x |     |x |x |x |x |x |x |        |x |x |     |x |x |x |x |x |x |
+--+--+--+--+--+--+--+--+--+--+--+--+  +--+--+  +  +--+--+  +  +  +  +  +  +
|x |                                |  |x    |  |  |  |  |  |  |  |  |  |  |
+--+  +--+  +--+--+  +--+  +--+  +--+  +--+--+--+--+  +  +--+--+--+--+--+--+
|x |  |x |  |x |x |  |x |  |x |  |x |  |x    |x    |x |x |   x |   x |   x |
+--+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+--+
levels 1, 3, 5, 7, 8, 10                levels 2, 4, 6, 9, 11


+--+--+--+--+--+--+--+--+--+--+     +--+--+--+--+--+--+--+--+--+--+
|  |x |  |x |x |  |x |  |x |  |     |   x |   x |x    |x    |x    |
+  +--+  +--+--+  +--+  +--+  +--+  +--+--+--+--+--+--+--+--+--+--+--+
|                                |  |  |  |  |  |  |  |  |  |  |  |  |
+--+--+--+--+--+--+--+--+--+--+--+  +  +  +  +  +  +  +  +  +  +  +  +
|x |x |x |x |x |x |x |x |x |x |x |  |x |x |x |x |x |x |x |x |x |x |x |
+--+--+--+--+--+--+--+--+--+--+--+  +--+--+--+--+--+--+--+--+--+--+--+
levels 1, 3, 5, 7, 8, 10             levels 2, 4, 6, 9, 11


11x12x16
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|     |                                |        |
+     +                                +        +
|     |                                |        |
+     +--+                             +        +
|        |                             |        |
+        +--+--+--+--+--+--+--+--+--+--+        +
|        |                             |        |
+     +--+                             +        +
|     |                                |        |
+     +                                +        +
|     |                                |        |
+     +--+--+--+--+--+--+--+--+--+--+--+--+     +
|        |                                |     |
+        +                                +     +
|        |                                |     |
+        +                             +--+     +
|        |                             |        |
+        +--+--+--+--+--+--+--+--+--+--+        +
|        |                             |        |
+        +                             +--+     +
|        |                                |     |
+        +                                +     +
|        |                                |     |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
(11 levels deep)

  

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Updated June 29, 2019.