Tetris Guideline

The Tetris guideline is the current specification that The Tetris Company enforces for making all new (2001 and later) Tetris games alike in form. The company revises the guideline annually. A mode labeled "standard" or just plain "Tetris" will adhere to the Guideline more closely than other modes.

Current rules, learned through observation of the behavior of authentic Tetris games, include:
 * Playfield is 10 cells wide and at least 22 cells tall, where the top two may be hidden
 * Tetromino colors
 * Cyan I
 * Yellow O
 * Purple T
 * Green S
 * Red Z
 * Blue J
 * Orange L
 * At least three next pieces visible
 * So-called Random Generator (also called "random bag" or "7 system")
 * Tetromino spawn locations
 * The I and O spawn in the middle columns
 * The rest spawn in the left-middle columns
 * The tetrominoes spawn horizontally and with their flat side pointed down.
 * Standard mappings for console and handheld gamepads:
 * Up, Down, Left, Right on joystick perform locking hard drop, non-locking soft drop (except first frame locking in some games), left shift, and right shift respectively.
 * Left fire button rotates 90 degrees counterclockwise, and right fire button rotates 90 degrees clockwise.
 * Super Rotation System (SRS) specifies tetromino rotation and lockdown behavior
 * "Hold piece": The player can press a button to send the falling tetromino to the hold box, and any tetromino that had been in the hold box moves to the top of the screen and begins falling. Hold cannot be used again until after the piece locks down. Games on platforms with fewer than eight usable buttons (such as the version on iPod) may skip this feature.

The combination of hold piece and Random Generator would appear to allow the player to play forever.

The extent to which the Guideline specifies the speed curve, the scoring system, and other aspects not listed on this page, is not known to the public.