Happy Cubes are a set of mechanical puzzles created in 1986 by the Belgian toy inventor Dirk Laureyssens. Happy Cubes are also known by a number of other names, among them: "Cube It!" cubes, "Wirrel Warrel" (in the Netherlands), "I.Q.ubes" and "Cococrash" (in Spain and Portugal). The Happy Cubes are made of 8mm-thick ethylene-vinyl acetate foam mats (also known as EVA). The tiles are based upon a 5x5 matrix where the outer squares may be present or absent. The central 3x3 kernel was fixed. Initially the puzzle is assembled into a 2-dimensional, flat 2x3 piece rectangle fitted into a frame. The basic challenge is to construct a perfect, 6-sided cube out of these 6 pieces. Usually, there is only one way to fit the pieces into a complete cube and it can be reached with various levels of difficulty by trial and error.