A geometric puzzle centered around geometric figures formed from unit-squares.
A polyomino is a plane geometric figure formed by joining one or more unit-squares edge to edge. Equivalently, a polyomino is a finite subset of the regular square tiling with a connected interior.
Typical examples of polyominoes are:
- the 2x1 dominoes (consisting of 2 squares)
- the straight 3x1 tromino and the L-shaped tromino (both consisting of 3 unit-squares)
- tetromino pieces (consisting of 4 squares), as used in TETRIS
- pentomino pieces (consisting of 5 squares); there are 12 pentominoes, up to rotation
- hexomino pieces (consisting of 6 squares)
By definition, polyominoes (consisting of 8 or more squares) may contain holes. For some puzzles (such as tiling problems), polyominoes with holes are inconvenient. Polyominoes without holes are called simply connected polyominoes.