A Particlely Nice Puzzle - XI

How many XI particles can occupy a small planer space?  Well, that all depends on the spin and orientation of each XI particle.

XI is a restricted opening 2D packing puzzle designed by Haym Hirsh and made by NothingYetDesigns.  The 2 openings in the top permit the XI and anti-XI particles to be injected within the frame.   The anti-XI particles are simply XI particles with a 180 degree spin.  Although the 2 openings conspire to suggest that both XI and anti-XI particles should be injected, it is not obvious how many of each is required or even if both types are needed.  Even if each anti-XI particle cancels out a XI particle as they bounce around and collide with each other, the odd number of particles suggests that the solution will eventually end up as a XI or anti-XI puzzle.  I leave it up to you to find out which.

Needless to say, the particles need to be added in a specific order and potentially rotated as they are entangled.  It’s nice that the top is clear so that you can see what you are doing.  Of course, you have to perform all those particle movements and rotations using the 2 openings.  Fiddly, but not that difficult.  However, if you regularly refer to your digits as sausages, you may find the physics of manipulating small particles more of a challenge.

XI is made with laser cut acrylic and has a nice heft to it.  The use of washers to elevate the clear top ensures that the 5 particles move nicely within the frame.  The puzzle information engraved on the top is also well done and useful for distinguishing the puzzle from other restricted opening 2D packing puzzles by Haym from NothingYetDesigns.