Contents > Introduction

Fundamentals

The playfield is the grid of square cells where Tetris is played. The standard playfield, shown below, consists of twenty visible rows and ten columns, but the dimensions are arbitrary.

Each playfield cell is in one of two states: empty or solid.

Tetrominoes—the falling pieces—are composed of four adjacent solid cells, painted any color. Each has a single-character, shape-based name:

A move is a rotation or a translation of the piece in play. The following terms apply to translation.

• A shift is a horizontal translation.
• A drop is a downward translation.
  • A soft drop is a player-controlled, one-row drop.
  • A hard drop is a player-controlled, drop as far down as the piece can go. The move locks the piece where it lands.
  • A gravity drop is an automatic, one-row drop triggered by the fall timer.

A move is preceded by a request to move. The game will deny a request to translate a piece out of bounds or into solid cells. If the game denies the fall timer’s request for a gravity drop, then the piece locks and the next piece spawns.

The rotation system determines if and how the game responds to a request to rotate. Modern versions of Tetris employ complicated rotation systems that take into account the states of the surrounding cells, the playfield boundaries, and other factors.

The randomizer is the mechanism that determines the sequence of pieces presented to the player.