Tetris Guideline

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

As of now, the Guideline is conjectured to encompass the following rules, learned through observation of the behavior of authentic Tetris games:

Indispensable rules

 * Playfield is 10 cells wide and at least 22 cells tall, where rows above 20 are hidden or obstructed by the field frame
 * Tetromino colors
 * Cyan I
 * Yellow O
 * Purple T
 * Green S
 * Red Z
 * Blue J
 * Orange L
 * Tetromino start 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.
 * Super Rotation System (SRS) specifies tetromino rotation
 * 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.
 * So-called Random Generator (also called "random bag" or "7 system")
 * "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.
 * Game must have ghost piece function.
 * Terms used in the user manual: "Tetriminos" not "tetrominoes" or "tetrads" or "pieces", letter names not "square" or "stick", etc.
 * Designated soft drop speed. Details vary between guideline versions.
 * Player may only level up by clearing lines. Required lines depends in the game.
 * The game must use a variant of Roger Dean's Tetris logo, although this was true from around 2000 - before the guidelines emerged.
 * Game must include a song called Korobeiniki. (Guideline 2005~)

Recommended but non-mandatory

 * Display of next-coming tetrominoes. Most games show at least three, though there are no hard rules.
 * Recognition and rewarding of T-spin moves. Conditions vary between guideline versions.
 * 2005: 3-corner T
 * 2006: 3-corner T no kick
 * Rewarding of Back to Back chains. Recognition method depends in the game.
 * Game should include the songs Katjusha, or Kalinka.

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

Although Guideline-compliant games share many traits, they also have differences in many aspects as well. There are a few instances where a game will break a trait which is shared by all other games thought to be compliant. Examples of this include the lack of the hold function and the T-spin's ability to start and continue Back-to-Back chains in iPod Tetris, and the inverted rotation button layout of TGM3 and TGM ACE. No explanations have been given for the reasons of these games' deviations.

Guideline Versions
Henk Rogers has been quoted as revising the guideline annually. This may only adhere to 2005 and later, as so far only guideline 2002, 2005 and 2006 have been known to be in existence, and guideline 2002 games have been built from scratch and released as late as 2005.

So far, the first confirmed guideline 2005 games (TGM ACE) has been released in December 2005, while the first confirmed guideline 2006 game (Tetris: New Century, although iPod Tetris released earlier behaves similarly) was released in September 2006. Therefore, it can be conjectured that the schedule of a new guideline version is released somewhere between the middle to the latter half of the year.

While many games have no publicly visible indication of the guideline version by the developer or publisher, some games have had their exact guideline versions made clear by them. They are listed in the Guideline compliant game differences page.