ξ Lattice by 小谷善行

The Xi Lattice (often stylized as ξ Lattice) is a high-level interlocking puzzle designed by Yoshiyuki Kotani, a prominent Japanese mathematician and professor at the Tokyo University of Agriculture and Technology.  Featured at the 19th International Puzzle Party (IPP19) in 1999, it is distinct from standard retail "Lattice" puzzles due to its specific mathematical construction and acrylic material.  Design & Mechanics Piece Configuration: It consists of 6 congruent pieces (all pieces are identical in shape). Target Shape: The goal is to assemble the pieces into a 7×7×3 grid structure featuring 4 internal holes. Difficulty: It is mathematically complex, with 164 possible assemblies but only 4 unique solutions. Movement: The solution requires a sequence of moves to lock the final pieces, typically rated at a maximum of 3.1.2 moves for the final assembly phase.  Designer Context Yoshiyuki Kotani is a founding member and current president of the Japanese Academy of Recreational Mathematics. His puzzles often lean into combinatorial and geometrical challenges. If you are interested in his other work, he recently published a book titled "Tasty Japanese Morsels in Recreational Mathematics" which includes various grid and logic puzzles.  Availability As an IPP exchange puzzle, the original acrylic version is rare and primarily found through specialty auction sites like Puzzle Paradise.  Would you like to explore the mathematical breakdown of its 164 assemblies, or are you looking for similar IPP puzzles from that era? The original design was a 6 piece selection of the entire 14 possible conformation of the notches. this model is the entire set of 14. The possible selections are listed in the excel file attached. all solutions require at least one A or I piece. (which are the dark purple ones in the print profile)