The Tetris Guideline is a yearly specification which The Tetris Company stipulates for developing new Tetris titles from 2001 and onward, beginning with Tetris Worlds. The reason for creating a guideline was to standardize Tetris play. Anyone around the world can pick up a new Tetris game and know how to play it. It was originally called "What is Tetris?", and is developed by Blue Planet Software. The rules are decided by a committee, with Alexey Pajitnov having the final say. In later years, summits were held to discuss the Tetris Guideline with other developers.
The Tetris Company's relationship with the guideline has changed over the years. Once requiring all new games, even re-releases to include a guideline compliant mode.
In 2011 a copy of the Tetris Guideline was leaked, dating to 2009. It is likely that the Guideline has been modified since that time, but most of the rules specified are still followed by new releases.
As of 2018, the Tetris Guideline is thought to have the following rules, taken from interviews, the leaked document, and by observing the behavior of authentic Tetris games:
- The game must use a variant of Roger Dean's Tetris logo, although this was true from around 2000 - before the guidelines emerged. The guideline contains rules for the use of the logo and what modifications are acceptable.
- Super Rotation System
- Super Rotation System (also known as SRS) specifies tetromino rotation and wall kicks. SRS defintes 5 points of rotation, each with a different purpose.
- Visual rotation - The natural rotation of a tetromino.
- Right/Left wall kick - Kick off an obstruction on the right or left.
- Floor kick - Kick off the floor, for when a tetromino has landed. Without kicks no rotation would be possible in some cases.
- Out of right well kick - If a tetromino is in a well, it can be rotated out.
- Out of left well kick - If a tetromino is in a well, it can be rotated out.
- Additionally, all rotations are reversible, if one is possible, the opposite is also possible. This is what allows T-Spin Triples to exist with the "Left out of well kick". There may be an option to disable wall kicks.
- Tetromino starting positions
- Tetrominoes appear on the 21st and 22nd rows of the playfield, centered and rounded to the right when needed. They must start with their flat side down, and move down immediately after appearing.
- Lock Down
- There are three types of Lock Down defined by the guideline, Infinite Placement Lock Down (or infinity), Extended Placement Lock Down (or move reset), and Classic Lock Down (or step reset). A piece has 0.5 s after landing on the stack before it locks down. With infinity, rotating or moving the piece will reset this timer. With move reset, this is limited to 15 moves/rotations. Finally step reset will only reset the timer if the piece moves down a row. Some games have an option to change between 2 or 3 of these modes.
- Hold is a mechanism that allows the player to store the active piece in the hold queue for later use. Only one piece can be in the hold queue. If there is already a piece in the hold queue, and the player holds the active piece, they are swapped, and the piece resets at the top of the playfield, becoming the new active piece. Hold cannot be used again until the piece locks down. Some games don't have the required space to display a hold piece, or that lack the necessary amount of buttons, may skip this mechanic. The combination of hold piece and Random Generator allows the player to play forever.
- Piece preview
- The piece previews (known as the Next Queue in the guideline) show the player the next pieces that will come into play. Some games have up to six previews, and some the option to change the amount. The queue can either be displayed on the right or the top of the playfield, with the next active piece being the closest to the top of the playfield. Pieces should be displayed in their starting orientations.
- The playfield (known as the Matrix in the guideline) is 10 cells wide and 20 cells tall, with an additional 20 cell buffer zone above the top of the playfield, usually hidden or obstructed by the field frame. If the hardware permits, a sliver of the 21st row is shown to aid players manipulate the active piece in that area. Some games have a smaller matrix, such as Tetris Giant.
- Piece colors
- Colors correspond to the shape of the tetromino.
- Random Generator
- The Random Generator (also known as "random bag" or "7 bag") determines the sequence of tetrominoes during gameplay. One of each of the 7 tetrominoes are shuffled in a "bag", and are dealt out one by one. When the bag is empty, a new one is filled and shuffled.
- Ghost piece
- The ghost piece is a player aid that allows them to preview where pieces will fall to. It is usually semi transparent, and does not interact with the active piece in any way. There is sometimes an option to disable it.
- Controller mappings
- 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.
- Standard mappings different from console/handheld gamepads for computer keyboards
- Standard mappings for mobile keypads
- Standard mappings for remote controls
- Tetris Glossary
- Terms used in the user manual: "Tetriminos" not "tetrominoes" or "tetrads" or "pieces", letter names not "square" or "stick", etc. There are many other terms as well, most of them not used by this wiki, instead generic names are used.
- Marathon speed curve is based on that used in Tetris Worlds.
- Designated soft drop speed. Details vary between guideline versions.
- 0.5 second lock delay when gravity is less than 20G.
- Player may only level up by clearing lines. Required lines depends on the game. Players can chose the level they wish to start on.
- Game must include a version of Korobeiniki. Note that The Tetris Company holds a sound trademark on the variation of the song used in Tetris games.
- Game over conditions
- The player tops out when a piece is spawned overlapping at least one block, a piece locks completely above the visible portion of the playfield, or a block is pushed above the 20-row buffer zone.
- Scoring#Recent_guideline_compatible_games system, including Back-to-Back recognition rules
- Combo recognition
- Line attack garbage system in multiplayer.
- T-Spin detection
- T-Spin rules based on the 3-corner method, and T-Spin Mini rules based on the pointing side cell method.
Recommended but non-mandatory
- DAS no faster than Tetris Zone.  (However, some Japanese games blend the Guideline with the Sega tradition of 1G DAS: Tetris New Century, Kiwamemichi, and the TGM collection.)
- Marathon, Sprint and Ultra modes. In general Sprint and Ultra will only be omitted for hardware reasons.
- Game title should begin with "Tetris".
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 (or Kiwamemichi, depending on interpretation). No explanations have been given for the reasons of these games' deviations.
Henk Rogers has been quoted as revising the guideline annually. Known versions of the guideline include 2002, 2005, 2006 and 2009, 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. Mihara's blog has mentioned discussions on revising the guideline in 2008 and 2010. The leaked guideline is dated March 2009.
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.
Known or suspected modifications
- Buffer zone size (in 2002 versions, at least 2 rows)
- T-Spin and T-Spin Mini recognition rules
- 2005: 3-corner T
- 2006: 3-corner T no kick
- Lock delay: the 15 reset limit was specified by 2009 and present in Tetris Zone (2007), while earlier games are known to use unlimited resets instead.
- Rewarding of Back-to-Back chains. Recognition method depends in the game.
- Soft drop speed; Tetris Zone uses 20 times the current level's fall speed, while other games have different speeds.
- Scoring and combos were fixed some time after 2006.
- Guideline compliant game differences
- Tetris Worlds, Tetris Deluxe, and Tetris Zone, considered by many to be the "reference" implementations of the Guideline at the respective times of the games' releases.
- Tetris DS, another popular game that is compliant with the Guideline
- "Mr. Tetris". Blue Planet Software. c. 2007. Archived from the original on 2007-02-28. Retrieved 2019-09-10.
- "Tetris from the Top: An Interview with Henk Rogers". Nintendo World Report. 2006-04-06. Archived from the original on 2019-09-10. Retrieved 2019-09-10.
- "Chōshigawarui?" [Feeling bad?]. Mihara's sub Layer. 2008-03-17. Archived from the original on 2019-09-12. Retrieved 2019-09-12.
- "“Megadoraibumini” kaihatsu-sha intabyū kōhen de rain'nappu ya debaggu o kataru. Morete shimatta taitoru wa! ?" [Talk about lineup and debugging in the second part of the Mega Drive Mini developer interview. The title that leaked !?]. Dengeki Online. 2019-08-28. Archived from the original on 2019-09-12. Retrieved 2019-09-12.
- "History of Tetris®". Tetris. n.d.. Archived from the original on 2019-09-12. Retrieved 2019-09-12.