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. The simplest wall kick algorithm (for games with wall kicks) is, in effect, the one used in Tetris Worst, because it always forces 20G. Therefore if it is above the bottom, it is forced to drop to the bottom.

Another simple wall kick algorithm is aligning the pieces to left, and checking left kick to ensure right wall smooth rotation. This is Atari rotation.

Another simple 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 fail if neither can be done. Wall kicks increase the number of possible twists. Official Scratch Tetris uses a variant: one space up is also checked, then 2 right if I is vertical and next to left wall.

Other notable rotation systems that include wall kick or floor kick include the following:
 * The rotation systems of the domino based games Dr. Mario, Puyo Puyo, 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 flexible Super Rotation System used by games that follow the Tetris Guideline.
 * The rotation system of DTET, a fan game with an unarbitrary wall kick algorithm, but not floor kick
 * XRS which is a cross rotation system in tetris-ex
 * Tetris Best rotation system allowing most kicks (but not the ones that kick 3) - used in Tetris Best
 * Tetris Perfect rotation system, a fully SRS-compatible rotation system allowing all the kicks, used in Tetris Perfect
 * Any rotation system in NullpoMino that has a wallkick set (only the preset wallkick rules are allowed --one of the very few cases of NullpoMino not being customizable)

Data tables describing systems for a number of Tetris games exist in the source code of several fan games, such as Heboris Unofficial Expansion, syoboris or Lockjaw.