I fondly remember Soma from my childhood, when I had a red plastic model. Soma is composed of six tetracubes (polycubes made of four cubes) plus one tricube, and can be assembled into a thre-by-three cube. The picture above shows two sets of the a wooden version of Soma. Gamepuzzles.com sells a plastic Soma variant (the same puzzle but with slightly different numbering in the accompanying pamphlet), called Block by Block, that is made by Binary Arts . The lovely wooden versions I bought from 24Hours7Days lack any helpful booklet with building ideas, a definite minus as far as my son is concerned.