Wednesday, July 19, 2023

A Puzzle of Two Tales – Soma in Case

Soma in Case by Hajime Katsumoto

I hate it!  No, I love it!  No, I’m pretty sure that I hate it!  But it’s great!

Introducing Soma in Case.  This copy isn’t pretty like the one produced by Cubicdissection in 2018.  The quality of the 3D printed box is rough, poorly fitting, and ugly.  There are a lot of artifacts on the perimeters and places where the printer seemed to completely fail.  The pieces are made from Livecubes, which are great for quickly producing pieces, but unfortunately, only four prong pieces were used requiring the prongs to be cut off of one cube of every piece.  And even though the prongs were removed, the base where the prongs are mounted still sticks out from the pieces.  Ideally, each piece would have used 2 cubes with 2 prongs that can be mated to avoid exposed prongs that need to be trimmed.

My apologies to the maker of this puzzle for criticizing a good deed.  In the end, the construction of this puzzle accomplishes its goal of providing an opportunity to experience this excellent design by Hajime Katsumoto.  In fact, nearly all of the solve time was spent searching for the magical assembly using the pieces without the box.   The box is really only needed to verify piece restrictions and testing potential solutions (I use the term potential loosely here since several of the assemblies that I tried had no potential to evolve into a solution).

The style of the box was modeled after (or perhaps before, I really don’t know) the one built by Cubicdissection.  I find the style a bit odd, but it works.  I did like the choice of the top and bottom fill pattern used.

The pieces of the soma cube (3x3x3) consist of 27 cubes and the box is 3x2x5 which holds 30 cubes.  That’s 3 extra spaces!  But wait – there’s a cube attached to the underside of the lid.  Not only does this keep the lid from coming off, but its main purpose is to get in way of adding pieces to the box.  Only 2 empty spaces left.

2-Prong Livecubes

It doesn’t take much pondering to determine that the space directly behind (or in front depending on your point of view) the fixed cube needs to be empty.  Otherwise, the box would be bricked – and as hard as I tried, I wasn’t able to brick the box.  The remaining empty space could be anywhere

I must have discovered all the ways to assemble the pieces within the box that aren’t possible.  At least it felt that way.  The Cubicdissection description says there are Over 100,000 solutions, only one is assemblable.  Although as a frequent BurrTools user, I would have said over 100,000 assemblies but a single solution, the point comes across that it won’t be trivial.  In fact, I worked on this one for a long time before I finally found that needle in the haystack.

Of course, it’s not a random process where you have to try all assemblies.  You can narrow the search by knowing where one empty space is within the box and hypothesizing where the other could be.  The cube attached to the underside of the lid also restricts how pieces can be oriented within the box.  You quickly realize that the movement of the pieces is very limited within the confines of the box and that rotations are difficult to accomplish.

This copy of Soma in Case may not be the heirloom puzzle (defined as any puzzle that children are not allowed to touch but someday own) coveted by serious puzzle collectors, but I highly endorse the use of 3D printing, Livecubes, and other materials to experience excellent puzzle designs like this one from Hajime Katsumoto.