Abstract: A series of interrelated sets of tetrahedron blocks. Each set comprises twelve blocks capable of assembly into a rectangular parallelepiped using all twelve blocks, and is also capable of assembly into an eight-block pyramid and a four-block tetrahedron. The pyramid and parallelepiped of all sets are the same height. The tetrahedrons are preferably hollow and each of them has a magnet for each face, e.g., affixed to the interior walls of its faces, the magnets being so polarized that upon assembly into a cube or pyramid, the magnets of facing faces attract each other. Preferably, the blocks are colored in such a way that faces of the same size and shape are colored alike and each size and shape has a different color.

Abstract: A series of interrelated sets of tetrahedron blocks. Each set is capable of assembly into a cube with all the cubes being identical in size. Typically, there are at least three such sets, though there may be more; and when there are three sets, for example, one set contains twice as many tetrahedron blocks as the second set and four times as many as the third set. The tetrahedrons are preferably hollow and each of them has a magnet for each face, e.g., affixed to the interior walls of its faces, the magnets being so polarized that upon assembly into a cube or pyramid, the magnets of facing faces attract each other. Preferably, the blocks are colored in such a way that faces of the same size and shape are colored alike and each size and shape has a different color.

Abstract: A series of interrelated sets of tetrahedron Each set is capable of assembly into a cube with all the cubes being identical in size. Typically, there are at least three such sets, though there may be more; and when there are three sets, for example, one set contains twice as many tetrahedron blocks as the second set and four times as many as the third set. The tetrahedrons are preferably hollow and each of them has a magnet for each face, e.g., affixed to the interior walls of its faces, the magnets being so polarized that upon assembly into a cube or pyramid, the magnets of facing faces attract each other. Preferably, the blocks are colored in such a way that faces of the same size and shape are colored alike and each size and shape has a different color.