# Piece

A piece in Tetris and similar games is a geometric shape consisting of a set of blocks that is moved as a unit. A block is the part of a piece that fills one unit of the playfield. In some games, all blocks that make up a piece are colored the same; in others, especially falling piece games other than Tetris and its fan games, they are colored differently.

## Polyominoes

A polyomino is a piece made of one or more square blocks, where all blocks are connected through full coincident edges (as if squares on graph paper).

• A free polyomino is one that may be translated (moved about), rotated, or reflected. These are used in Pokémon Tetris.
• A one-sided polyomino is one that may be translated or rotated. These are the ones used in Tetris.
• A fixed polyomino can only be translated.

Polyominoes come in several sizes:

Larger sizes of polyominoes appear in Magical Tetris Challenge and some fan games. Combinos can generate arbitrary dodecominos (12-block polyominos). In addition, octominos can be formed in Sega Tetris by fusing two tetrominoes together.

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".

## Pseudo-polyominoes

Pseudo-tetrominoes
in Tetris 2

A pseudo-polyomino, also known as a hinged polyomino, polyking or polyplet[1] is similar to a polyomino but also allows connections at a point. In games that use pseudo-polyominoes, a piece may break apart at the diagonal connections when it lands, and the fragments may or may not be controllable afterward.

Larger pseudo-polyominoes appear in some fan games.

## Quasi-polyomino

An example of a quasi-tetromino

A quasi-polyomino is any set of blocks regardless of whether they are connected or not (as long as they are still aligned to the grid). These are featured in some fan games, such as Kowaris.

## Other polyforms

Polyhexes are pieces formed from regular hexagons. There are multiple Tetris-like games that use polyhexes, such as Hextris and Bikaka.[2] Bubble Bath Babes uses polyhexes that may be reflected around the X or Y axis but not rotated.

Polyabolos are pieces formed from right isosceles triangles. They are featured in the NES game Pyramid.

Polyiamonds are pieces formed from equilateral triangles.

## Polycubes

A polycube is a piece made of cubic blocks, where all blocks are connected through full coincident faces. These are featured in 3D variants such as Blockout and 3D Tetris.