Appendix - npincomplete/tetris GitHub Wiki

Terminology

Tetromino

A tetromino is a polyomino made of four square blocks. Tetrominos come in seven shapes, all of which can be rotated and then dropped. The seven one-sided tetrominoes are I, O, T, S, Z, J, and L. The spelling "tetromino" is standard among mathematicians.

Polyomino

A polyomino is a piece made of two or more square blocks, where all blocks are connected through full coincident edges.

  • A free polyomino is one that may be translated (moved about), rotated, or reflected.
  • A one-sided polyomino is one that may be translated or rotated.
  • A fixed polyomino can only be translated.

Polyominoes come in several sizes:

  • 2 blocks make a domino
  • 3 blocks make a tromino
  • 4 blocks make a tetromino
  • 5 blocks make a pentomino

Polyominoes are often named by a Latin letter that resembles the shape of the polyomino. For instance, an "I" has all its blocks in a straight line, and a "T" consists of an "I" tromino with one or more blocks in a straight line connected to one side of the center of the "I".