Wall kick

A wall kick happens when a player rotates a piece when no space exists in the squares where that tetromino would normally occupy after the rotation. To compensate, the game sets a certain number of alternative spaces for the tetromino to look. Wall kicks started appearing in games because after a piece would be backed up against the wall, it would awkwardly be unable to rotate until first moving back.

Here T can rotate

Here T cannot rotate without a wall kick

The simplest wall kick algorithm, used (with variations) by TGM rotation and several fan games in the same tradition, is to try moving the tetromino one space to the right, and then one space to the left, and then fail.

Other notable rotation systems that include wall kick and/or floor kick include the following:

• The rotation systems of the domino based games Dr. Mario, Puyo Pop, and Super Puzzle Fighter II.
• The rotation system of Tetris DX, which allows wall climbing
• The rotation system of The New Tetris, considered a predecessor to SRS
• SRS, the Super Rotation System used by games that follow the Tetris Guideline
• The rotation system of DTET, a fan game with a complex but unarbitrary wall/floor kick algorithm

Koryan as well as Jagorochi researched the SRS system thoroughly and made diagrams of how SRS finds wallkicks.

The complete system for a number of Tetris games exists in wktables.c within the open-source fan game Lockjaw.