Wednesday, June 19, 2019

A Puzzle with No Name – Yukari’s Cube

Yukari's Cube - Pieces
Yunichi and Yukari Yananose are the owners of the Pluredro puzzle shop in Australia.  They offer high end puzzles designed by the extraordinarily talented Yunichi.  In addition to the Pluredro blog on the puzzle shop’s site, Yukari maintains a very nice blog of her own, Random thoughts with my puzzle sense.  The most recent post on Yukari’s blog, Freshly made puzzle with no name, described a new puzzle designed by Yunichi that was hot off the press.  So hot in fact that it had yet to acquire a name.

Most of my designs are named No Name, blank, space, or whatever your favorite term is for an unfilled spreadsheet cell used to contain a puzzle’s name.  It seems that my creativity process shuts down after the puzzle design is complete.  My first few puzzle designs were lucky to have been named by my wife (Eviction, Confusion, Secret Garden, The Couch, The Maze).  Some later puzzles were named after the wood used to make them by the craftsmen who made them as a way to identify them (Pink Ivory Ring, Multiwood).  Even others were named for their warm reception by the puzzle community (Reject #1, Reject #2, Reject #3).  I completely empathize with puzzlers that collect puzzles with no names.  Around our house, we refer to Yunichi’s new puzzle as Yukari’s Cube.

Yukari's Cube - The Present
The Little Present
After seeing the intriguing set of pieces designed by Yunichi, I did what any sane puzzler with wood and wood mangling equipment in the garage would do.  I went out and mangled some wood.   I glued up 9 corners made with 3 cubes each and then worked on the angled edges.  No sissy jigs on a table saw for me.  I used my beveling jig on the sander to obliterate vast quantities of wood into billowing clouds of swirling sawdust.

Since Yukari didn’t provide a picture of the puzzle in the solved state, I wasn’t sure if the cube was solid (easier), had holes (more difficult), required odd angles (even more difficult), or was a completely cosmic cubic space created by an insanely convoluted wooden shell (who comes up with these crazy ideas kind of difficulty).  I didn’t even know if you could make a cube with 9 corner pieces before all the angled cuts are added.  The 9 corner pieces are made with 27 cubes, the same as a 3x3x3 cube, which is a good first indicated that it might be possible.  I decided to test that out first.  I found out that … well you should figure that out for yourself.  I’d hate to be the despoiler of frustration (i.e., fun).

Yukari's Cube - Pagoda
Even my wife liked the puzzle, I know that she liked it because she was shuffling the pieces around muttering curses under her breath.  This is how puzzlers show appreciation for good designs.

My 5 year old grandson, not one to be constrained by complex geometric shapes like cubes, set out to design his own solution and built an abstract pagoda.  We even built a little present complete with bow.

Yukari was right in pointing out that many puzzlers will be able to solve this relatively quickly.  Yukari alluded to a little trick, but from my perspective, I think that there are 2 that you need to overcome.  Unfortunately, I can’t mention them here without spoilers.  It took me about 10 minutes to construct the cube, which included the time spent on deciding what the cube looked like.  However, I half expect someone to eventually tell me one day, “That’s not the solution”. 

Yukari included the sad disclaimer that there is no plan to produce this puzzle but I wouldn’t be surprised if Yunichi had some puzzling tricks up his sleeve to add to this puzzle.   Maybe someday it will become one of Yunichi’s groovy puzzles or the core of a grander undertaking.  Keep your eye on the Pluredro shop.


  1. My favourite tromino-L cube is TRILOGIC by Roland Koch.
    Those cubies remind me of licorice cubes, the wonderful candy.

    1. I'm assuming that the TRILOGIC goal is to construct a cube with a symmetric pattern on all sides. I wonder if an analysis been done on all the ways to combine the licorice cubes into L pieces and then to create specific patterns on the solved cube.

    2. Well, there are only three ways to make tromino-L pieces from the licorice cubes. For symmetry on all the faces, there are relatively few solutions, as I discovered way back in 2011. {1+2+6, 1+3+5, 1+4+4, 2+2+5, 2+3+4, 3+3+3}. You might enjoy checking it out on your own, but I can always supply you with my results, if you wish. -Tyler.

    3. Two more notes:
      - When I list {1+2+6, ...} above, these numbers are the distribution of the three type of "checkered" L pieces. Each of the piece distributions can be permuted. 1+2+6, 2+1+6, 1+6+2, and 2+6+1 each have 2 checkered solutions on all the faces; 6+1+2 and 6+2+1 both have no checkered solutions. (I leave it to you to determine how I have identified the pieces.) The six families of piece distributions cover 25 distinct cases. The other 19 cases have from 4 to 74 solutions with checkered patterns.
      - There are four other ways to make L pieces, not checkered as the first three pieces, and adjacent cubies are not oriented the same. Thanks for wondering about "all" the ways to combine licorice cubes, as I had not done that before now. I have found some neat new results with the new L pieces. I look forward to comparing notes. You have my email.