Abstract: The four elements are each provided with protrusions constituted by forks the branches of which are resilient, which are each provided with a recess and with an embossment. These protrusions engage with each other, their embossments and their recesses hooking each other, and are thus articulated to each other around rotation axes. The series of protrusions and of the free spaces which separate them are determined in such a way that the four plates can be articulated to each other two by two, that has for consequence they can be articulated all the four to each other. With respect to a central axis, the half-series of each element are not symmetrical but they can be identical.

Abstract: Four elements are each provided with protrusions constituted by forks, the branches of which are resilient. Each fork is provided with a recess and with an embossment. The protrusions engage with each other, their embossments and their recesses hooking each other, and are thus assembled to each other around rotation axes. The series of protrusions and of the free spaces which separate them are arranged in such a way that the four elements can be articulated to each other two by two, that has for consequence they can be assembled together by engagement of the protrusions of any one element with those of another element. The protrusions on respective halves of each element are not arranged symmetrically, but they can be identical.

Abstract: Regular rhombic dodecahedrons having faces with two aspects of two different kinds, each belonging to a same family, one by a bare surface, the other one by a shaded surface, are piled on a base having nests allowing those polyhedrons to be placed on top to build a composed pyramid. The general configuration of the visible faces of one kind and of the other kind will respond to specific rules of the game.