Icosoku

Icosoku is a mechanical puzzle invented in 2009 by the Italian designer Andrea Mainini and manufactured and sold by the Dutch company Recent Toys International. The puzzle takes the form of a blue plastic frame shaped like an icosahedron, a twenty-sided solid, holding twenty white triangular tiles and twelve yellow numbered pins at the corners where five triangles meet. Each triangular tile carries a pattern of black dots on its surface, and the player removes and repositions the tiles within the frame, choosing both their placement and their rotation. The goal is to arrange every tile so that, at each of the twelve numbered corner pins, the dots on the five triangles meeting at that pin add up to the number printed on the pin itself. The manufacturer states that every possible arrangement of numbered pins that ships with the puzzle has at least one valid solution, making it a solvable rather than merely decorative logic puzzle, and the design won multiple toy and puzzle awards in the year following its release.