Somacube invented in 1936 by the Danish author and inventor Piet Hein.
Piet Hein realized that two cubes can only be united in a single dimension, to a composition with three cubes can add another dimension perpendicular to the first and that it needed a fourth cube to get a third dimension perpendicular to the first two.
This puzzle you can make an unlimited number of characters. You get a large number of characters that you can do with the SOMA cube.