A New Spin on Puzzling - Tetra Spinner

“That’s a novel take on packing tetrominoes”.  That was my initial thought when I saw Tetra Spinner while perusing the IPP39 Nob Yoshigahara Puzzle Design Competition entries.  I was intrigued and looking forward to trying it.

Tetra Spinner was designed by Yasuhiro Hashimoto and Mineyuki Uyematsu and was one of the top ten vote getters in the competition.  I got my chance to try it at the Rochester Puzzle Picnic (A Decade of Puzzling - RPP 2019).

It’s made from plexiglass and consists of a frame and all 5 tetrominoes (i.e., the free ones and not the extra 2 one-sided ones).  Tetrominoe is just a fancy name for a connected shape made from 4 squares in a plane.  Each of the tetrominoes in Tetra Spinner is a different color making it an eye catcher.  However, it’s the frame that gives this puzzle it’s unique appeal.  The frame is comprised of 3 layers of plexiglass.  The outer 2 layers are clear and bolted together through the center.  There is a spacer in the middle around the bolt to keep the two outer layers apart.  The middle layer has the same dimensions as the outer layer but most of the interior has been removed to make room for the tetrominoes.  The center layer can be moved and rotated around the middle but is restricted by the spacer holding the outer pieces.

The objective is to place the five tetrominoe pieces in the middle layer so that the middle layer is centered within the puzzle.  This requires that you move the white plexiglass frame as far as it will go so that you can add pieces to the empty areas that now hang outside the outer layers.  However, the more pieces that you add, the more difficult it is to move the frame of the middle layer.  This requires determining where the pieces need to go within the frame and the order that they need to be added.  Oh, and while you’re doing that, you need to determine how the pieces and frame need to be moved around to accomplish all that.

I didn’t find this puzzle difficult but it was fun to solve.  I didn’t include the photo of the puzzle in the solved state, since it would give away part of the solving process.  It would certainly give away the first piece that would be removed although this should become obvious rather quickly in the solving process.  Yes, that was a hint, but I’m sure you were already thinking about it.  It’s only cheating if you go back 2 sentences and reread it to understand it.

S,Z,J,and L Tetrominoes

Before concluding, I feel compelled to explain the reference to free tetrominoes to save readers the embarrassment of getting caught leaving the puzzle store without paying for tetrominoe related puzzles.  There are 5 tetrominoes if you regard the pieces irrespective of orientation.  These are referred to as free tetrominoes.  There are 7 tetrominoe shapes if you are not allowed to turn them over.  These are referred to as one-sided tetrominoes.  The difference between the free tetrominoes and the one-sided tetrominoes is due to the 2 pieces that can be flipped over to provide a different shape; the S piece becomes the Z piece and the J piece becomes the L piece.