Arika Rotation System

Arika Rotation System (also known as ARS) is a gameplay mechanic used in the Tetris: The Grand Master series and Tetris with Cardcaptor Sakura Eternal Heart, and is derived from Sega's rotation system. Many fan games also implement this rotation system.

Games using Arika Rotation System 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

The basic rotations inherits their properties from Sega rotation, which was used in many other Japanese 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 state of the T, L, and J tetrominoes downward.

TGM's basic rotations.

Wall kicks

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, from their 3-wide orientations, will not kick off their center column. In the situations illustrated below if the marked block is occupied.

However, there are very similar situations where additional off-center blocks will enable a wall kick, due to a bug in the way blocks that block a rotation are detected. In the situations illustrated below, the upper blocks are off-center and enable the kick even in the presence of blocks in the center column.

Clockwise rotation will successfully kick:

Counter-clockwise rotation will successfully kick:

Those situations successfully kick, because the algorithm for checking blocking blocks searches in the following pattern:

If the first block found in the search is a center column block, the rotation is blocked. But if the first block found isn't in the center column, and a kick is possible, then a kick is applied.

Wall kicks added in Tetris The Grand Master 3 Terror-Instinct

I-piece wall kicks

In Terror-Instinct, the I-pieces can kick walls and the stack. There are two different wall kicks.

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

Similarly to floor kicks, the I-piece needs to be touching part of the stack to kick one cell to the right.

Try to rotate	Basic rotation fails	No rotation occurs
Try to rotate	Basic rotation fails	Kick right

I tetromino's floor kicks

The I tetromino can kick the floor, but it can be performed only once and 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, up to two times.

Try to rotate

Basic rotation fails

Kick up

Rotating a T or I tetromino after it has floor kicked will permanently set the lock delay for that tetromino to zero. This is actually what prevents the second I floorkick. After the second rotation is processed, movement gets processed, allowing a shift of one cell left or right if it's done fast enough. Gravity is then applied. If the I tetromino is not in contact with an occupied cell below after processing gravity, any attempt to floorkick will fail, as explained above. If contact does exist, the tetromino will instantly lock down, preventing rotation from being processed at all.

The T tetromino has no such restriction, so it IS possible to make it floor kick twice, but it will lock after the second one because there is no way to process rotation again before it locks.

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 in the other hand, does not.

Firm drop

Rotate right

Kicks to here

A block (marked as red) is required for the piece to do so.

Firm drop

Rotate right

This fails too

Kicks to here

ACE-ARS and ARS2

Ace's rotation is a hybrid of SRS and ARS. Ace features guideline colors and lock delay is now directly reset by rotation/movement. A maximum of 128 lock delay resets are permitted per piece. Piece spawns that would previously have resulted in death (blocks occupying row 19/20 spawn locations) will now instead cause the piece to spawn higher, to a maximum of rows 21/22. This effectively makes the usable well size 2 rows higher.

ARS2 is available through an Xbox live patch for the game. Normal ARS features Sonic Lock (locking hard drop) and non-locking soft drop. ARS2 reverts these drop mechanics to how it worked in TGM3 and TGM2.

See also

• Sega Rotation
• Tetris Plus 2: The first game to use wall kicks with a Sega-like rotation system.

References

• KAN's detailed explanation of TGM3's new I and T floorkicks