TGM Rotation

TGM rotation is a game play mechanic used in Tetris The Grand Master and other Arika tetromino games, derived from Sega rotation. It is often refered to as ARS (Arika Rotation System), even though some people believe that this name is misleading.

Games using TGM rotation generally use IRS, fast DAS, lock delay, and firm drop, and tetrominoes start out with the topmost block on the top row (generally row 20). The "ARS" and "ARS2" modes of Tetris The Grand Master Ace use a hybrid of TGM rules and Guideline rules.

Basic rotation

TGM's basic rotations inherits most of its properties from Sega rotation, which was used in most previous Japanese arcade Tetris games. Some defining characteristics include:

• Having 2 (as opposed to 4) rotation states for S, Z, and I tetrominoes.
• Keeping tetrominoes at an even level while rotating to always allow rotation when the tetromino is on a flat surface (except for the I tetromino - see exceptions below).
• Pointing the initial stance of the T, L, and J tetrominoes downward.

TGM's basic rotations.

Wall kicks

TGM pioneered the use of wall kicks, with simple but effective kick rules. These rules were unchanged until TGM3, remaining constant across TGM, TA, TAP, and Sakura Tetris. Up to 3 locations are tried, in this order, before rotation will fail:

• Basic rotation
• 1 space right of basic rotation
• 1 space left of basic rotation

In addition to these rules, there are some extra exceptions where certain wall kicks are not allowed:

• The I tetromino will never kick.
• L, J, and T tetrominoes will not rotate in the situations illustrated below if the marked block is occupied.

• However, L tetrominoes will rotate clockwise and J tetrominoes counterclockwise in the situations illustrated below if both the marked blocks are occupied.

New wall kicks in TGM3

I tetromino's wall kicks

In TGM3, the I tetromino can kick walls. There are 3 different types of wall kicks.

Try to rotate	Basic rotation fails	Kick 1 space right
Try to rotate	Basic rotation fails	Kick 2 space right
Try to rotate	Basic rotation fails	Kick left

I tetromino's floor kicks

The I tetromino can kick the floor.

Notes:

• Like hold piece, floor kick can be performed only once per tetromino.
• The tetromino cannot kick the floor in mid-air.

Fail

OK

OK

There are 2 different types of floor kicks.

Try to rotate	Basic rotation fails	Kick 1 space up
Try to rotate	Basic rotation fails	Kick 2 space up

T tetromino's floor kicks

The T tetromino can escape from a hollow.

Notes:

• This action can be performed only once per tetromino.

Try to rotate

Basic rotation fails

Kick up

Right side bias

In TGM's rotation system, the Tetrominoes rotate on only one axis resulting in asymmetrical rotations. In this example, the I piece can't rotate on the left side of the stack;

A situation which would work on the right side.

Notice the I has 1 rotation axis;

I piece's rotation axis

This case does not apply to the T tetromino, as it rotates on its center;

T rotation axis

Mihara's conspiracy

Due to the right side bias with wall kicks, doing this move with a J when there is an empty hole right of the block that the J is caught on will lead to a hole.

L works:

Firm drop

Rotate left

Kicks to here

J does not...

Firm drop

Rotate right

Kicks to here

...unless there is another block to force a kick to the left.

Firm drop

Rotate right

This fails too

Kicks to here

It can however be used to the player's advantage by it being used to jump over spikes.

ACE-ARS and ARS2

ARS was required to be featured as a Xbox live download for ACE due to the Tetris Guideline.

Ace's rotation is a hybrid of SRS and ARS. Ace features guideline colors and allows 128 rotations and 128 movements (Rather than true infinity). ACE features the ability to floor kick with any block, but still retains the wall kick rather than floor kick behavior from the original TGM rotation.

Normal ARS features Sonic Lock (locking hard drop) and non-locking soft drop.

ARS2 has Firm Drop (non-locking hard drop) and soft drop (locking).

To-Do

• describe ACE's ARS and ARS2?
• add more visual aids?

References

• KAN's detailed explanation of TGM3's new I and T floorkicks
• TGM rotations, in Japanese