For more advanced players, please go here: T-Spin Methods.

There are some games that give scoring rewards for twisting a tetromino into a tight space. When this is done with a T tetromino, it is called a T-spin.

Two basic algorithms, with slight variations, have been used in newer games to detect and reward in-place spins:

Immobile, used in The New Tetris, Tetris Best, Tetris Best 2 and Tetris Perfect/Return: A twist is recognised if a tetromino locks in a position where it cannot move left, right, or up. In The New Tetris, there is only a reward if rows are completed in this way. In Tetris Best, Tetris Best 2 and Tetris Perfect, sliding diagonally (by pressing left or right to move to tight space) also counts as spin. Example:

Immobile T-slot

Entry

Rotated to a position of immobility, and a row will clear

3-corner T, used in Tetris DS and other SRS based games: A T-spin bonus is awarded if all of the following are true:^[1]
1. Tetromino being locked is T.
2. Last successful movement of the tetromino was a rotate, as opposed to sideways movement, downward movement, or falling due to gravity. (Canceling lock delay in games that allow it, such as Tetris DS, does not count as a movement.) The tetromino doesn't even have to end up in a different orientation than it was dropped in; setting up the WKT below in Tetris Worlds or Tetris DS and pressing both rotate buttons (B–A or A–B) will trigger the T-spin bonus even without any net rotation.
3. Three of the 4 squares diagonally adjacent to the T's center are occupied. In Tetris DS, the walls and floor surrounding the playfield are considered "occupied", while in Tetris Worlds for GBA, they aren't. Example:

3-corner T-slot

Entry

Rotated and 3 corners are occupied in the 3x3 box which contains the T

Different games add further restrictions:

3-corner T no wall, used in Tetris Worlds: The walls and floor surrounding the playfield are not considered "occupied". This means that if a wall kick places the T tetromino with its flat side against the wall or floor, the T-spin will not be recognized. (Kicks that place the flat side against blocks in the playfield still work.)
3-corner T no kick, used in Tetris: New Century, iPod Tetris, Tetris Evolution, and most other official guideline games released after 2006: The final rotation must not involve a wall kick, that is, it recognizes only the WKT below.
Tetris Zone recognizes T-Spins that involve a wallkick, but will only recognize any T-Spin that results in a Single or Double line clear. When performing a T-Spin Triple in Tetris Zone, it counts as a regular Triple line clear.

Rewards

Rewards for T-spins first appeared in The New Tetris. The game added a reward for T-spins (and for twists involving other pieces), which would trigger an "avalanche." Tetrisphere product coordinator Ken Lobb is credited for inspiring T-spin rewards.^[2] Henk Rogers implied that it was the mobile game Tetris Battle that inspired the T-Spin's current dominating points and garbage rewards^[3], although T-Spins in a nerfed form found their way into prior guideline games such as Tetris Worlds. As of 2006, the Tetris Guideline seems to favor T-spins that don't involve a wallkick.

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T-Spin Mini

A T-Spin Mini, also called EZ T-Spin in Tetris Zone, is generally referred to as a T-Spin with no lines or with one line clear (T-Spin Mini Single) achieved with a wall kick. These spin bonuses are less powerful than their "proper" counterparts. However, depending on the game, some cases such as the following are treated as "proper" T-Spin, even though they are using wall kicks.

case A. Standard T-Spin Single with a wall kick

case B. A T-Spin Single achieved with a T-Spin Triple twist

In addition, some games treat the following T-Spin as Mini even though it does not use any wall kicks.

case C. A T-Spin Single with a hole behind the T

Tetris DS (Singleplayer)

In Tetris DS Singleplayer modes, cases A and B are treated as a T-Spin Mini because the game checks only whether the player has used a wall kick or not. Since case C does not use any kicks it is treated as a proper T-Spin Single.

The game does not differentiate between the T-Spin Singles (both Regular and Mini) in Multiplayer modes.

Tetris Online (Japan)

The game treats case A and C as a proper T-Spin Single but case B as a T-Spin Mini Single. When a T piece is locked, the game consider the spin as a mini if the cell behind the T piece (the cyan block in the following diagram) is filled with a block or floor.

Tetris Friends

Cases A and B are treated as proper T-Spins, but C is treated as Mini. The exact rule of T-Spin Mini in this game is overly complex. ("What a T-Spin Mini is and why they are so confusing" by Kitaru)

Cells next to the pointing side of T

When a T piece is locked, the game checks if the cells next to the pointing side of T (shown as red blocks in the following diagram) is filled. The game treats the spin as a Mini if only one of these two red cells are filled. If both cells are filled then the spin is a proper one.

T-Spin Triple Wall Kick Upgrade

If the T piece is kicked using the T-Spin Triple wall kick (The last kick test in SRS, with the orientation 0>>1 or 2>>3) then the spin is automatically "upgraded" to proper status, disregarding the prior cell checks.

Tetris Party Deluxe

Cases A and B are treated as proper T-Spins, but C is treated as Mini. This game also detects T-Spin Mini Double.

NullpoMino

This game emulates the behavior of Tetris Online (Japan) if the spin option is set to T-Only (treats cases A and C as proper and case B as Mini) and Tetris Party Deluxe if set to All (treats cases A and B as proper and case C as Mini).

Types of T-Spin triples

Right

Only the right T-spin Triple works in SRS. You can't reverse the overhang. That is why it is called the right T-spin triple.

T-Spin Triple

Wrong

Tetris Best, Tetris Perfect and Tetris Return:

T-Spin Triple

Tetris Perfect and Tetris Return only:

T-Spin Triple

(for the last one, the block highlighted in red is needed)

You can also do a mirror image of each setup. For the first two, it can also be done from the other side of the T (!). These are shown in the next section.

Crazy

These are the craziest T-spin triples.

T-Spin Triple