Tetra-Claw

Tetra-Claw was designed by Derek Bosch and entered in the Nob Yoshigahara Puzzle Design Competition at the 41st International Puzzle Party.  I was certainly lured into attempting to solve it in the design competition room but alas, it wasn’t a quick solve and there were so many other tempting puzzles to look at.  Lucky for me, Steve Nicholls 3D printed a large batch for Derek to use as his exchange puzzle, providing me with the opportunity to solve it at my leisure.  And leisure I did!  I took it apart rather quickly but the 4 pieces had morphed into an artistic pile that graced a dining room shelf for an extended period of time.  We even had parties to celebrate the anniversaries.

Of course, I hadn’t been putting it off solving it because of commitment issues or that it looks daunting.  I was just waiting for the right time.  Which happened to happen yesterday.  After second breakfast.  While taking a break from being repummeled by an innocuous looking 2D sliding puzzle.

Tetra-Claw consists of … wait for it … 4 Claws!  The 4 claws each have 3 prongs that become entangled to make something regularly tetrahedronish.  When solved, each piece touches all the prongs of the other pieces.

To make the puzzle challenging, Derek has added pins and mazes to the prongs of each piece so that there is a non-trivial path that must be taken to solve the puzzle.  Every pair of pieces has a pin-maze interface that defines it’s movement.  That’s 6 mazes that have to be simultaneously traversed.  The pins and mazes have been allocated to the pieces to make them all unique with one piece being all male (pins), one all female (mazes), and the other 2 can’t totally commit with one leaning towards mostly male and the other towards mostly female.

As daunting as it seemed, there did seem to be a good way to start and it didn’t take long to have 3 pieces locked in place.  And I felt confident that they were in the correct placement.  The problem was adding the 4th piece, which had 3 ways that it could be inserted.  It was obvious to me that I was probably not not going to be able to determine which one just by studying the mazes.  So I made an executive decision to simply try all three.  Of course, each required a lot of piece movements to determine whether they would all come together or not. And after trying 4 or 5 of those 3 orientations, I finally had a nicely solved Tetra-Claw.

The other semi-permanent puzzle art fixtures on the dinning room shelf are going to miss their buddy.  

Karakuri Packing

I’ve been wanting to try Karakuri Packing for a while now and I recently had to the opportunity to acquire one from a kind soul on the Mechanical Puzzle Discord (MPD).  Now I can see why others gave it high marks and why it received a Jury Honorable Mention award in the Nob Yoshigahara Puzzle Design Competition at the 40th International Puzzle Party (IPP).  It’s so good! 

Karakuri Packing is a 3D apparent-cube, restricted-opening packing puzzle designed by Yasuhiro Hashimoto.  It consists of 5 pieces that need to be packed within a 3x3x3 box.  The pieces are comprised of 26 voxels leaving 1 voxel unaccounted for.  Oh, what could that mean?  Well, one piece has a dowel sticking out less than a width of a voxel.  But there are also 5 holes drilled into the pieces and 2 additional dowels that have to be packed as well (yes, yes, you can argue that there are really 7 pieces that have to be packed in the box).  Each of the free dowels is just short of 2 voxels.  5 holes and 5 voxels’ worth of dowel.  Coincidence or trap?

To complete the challenge, the box has a 2x3 voxel opening on the top.  For the version that I received, the 1x3 voxel lip on the box is removable which allows the pieces to be packed in an incorrect configuration.  Or you could store it in the correct configuration and be able to dump and scramble the pieces without seeing how they would emerge from the box.

Attempting to determine what novel ideas could be used, I brainstormed some that were not used.  But more importantly, there were moves that I didn’t anticipate.  I was very happy to see these unexpected interactions.

My solve was done in 2 short sittings, The first to convince me that it wasn’t going to be easy.  The second to show me that it wasn’t as difficult as my impression from the prior attempt.  Although there are many assemblies, there are things that reduce the complexity such as the opening restricting the orientation of the pieces and holes needing to be aligned to support the dowels.  Definitely a fun puzzle and I wouldn’t mind seeing other puzzles in this format.

Although I’m very late to the game with Karakuri Packing, others have blogged about it in a more timely fashion like Allard and Kevin.