Message #3665

Subject: Re: Physical 4D puzzle achieved
Date: Tue, 21 Feb 2017 13:22:46 +0000

I think, it has never been impossible to build a 4D puzzle in 3D space, just that it is hard to satisfy all of those requirements:

  1. It is a twisty puzzle with moving physical parts (unlike Rubik’s Tube or Rubik’s Touch Cube)
  2. It is easy to twist
  3. It is similar to the "natural" puzzle.

About (2) I think, unless you try making a prototype and twisting it you won’t know if it is easy to twist. However I guess my old 2^4 model does not satisfy that requirement.

Your puzzle satisfy (1) and (3) (I prefer that the red cube = left, blue = right and black = top, that is more similar to MC4D UI) but does not satisfy (2) for some twists. They are, in fact, crucial twists that make the puzzle 4D.

If any twist that is probably easy to do in 3D but is impossible in the 4D natural puzzle, we should not include it (like the "turning the inner 2x2x2 black face" without reorientation or the "jumbling move") otherwise it would no longer be 2^4.

This may be able to explain the reason why some twists, especially the red/blue sticker switch, is hard:
<attached images>

Also, at first I didn’t think magnet position is worth discussing, until I realize that we can’t make a group of objects that attract one another only by magnets.