 The video game Tetris is based on the seven one-sided tetrominoes (spelled "Tetriminos" in the game), and the board game Blokus uses all of the free polyominoes up to pentominoes.The word "polyomino" and the names of the various orders of polyomino are all back-formations from the word "domino", a common game piece consisting of two squares, with the first letter "d-" fancifully interpreted as a version of the prefix "di-" meaning "two.