Games using Arika Rotation System generally use IRS, fast DAS, lock delay, and sonic drop. Pieces usually appear in the 20th and 19th row, unlike guideline games which appear in the 22nd and 21st rows. The "ARS" and "ARS2" modes of Tetris The Grand Master Ace use a hybrid of TGM rules and Guideline rules.
Tetris with Cardcaptor Sakura Eternal Heart uses a modified version of ARS that does not have Mihara's conspiracy.
The basic rotation states of pieces is identical to Sega rotation, which was used in older Japanese Tetris games since 1988.
Some defining characteristics include:
All pieces except for the I-piece have its rotation states aligned towards the bottom of the piece's bounding box. This allows a piece to rotate after landing on a flat surface, without requiring floor kicks.
I, S, and Z-pieces only have two states, and rotating in either direction simply toggles their state.
Unlike Sega rotation, L, J, and T pieces can be rotated both clockwise, and counterclockwise.
The initial state of the L, J, and T-pieces have their longest flat side facing up.
Arika Rotation System's basic rotations.
Kicks
When basic rotation fails due to the piece colliding with the edges of the playfield or the stack, two kicks are tested.
The process is as follows:
Basic rotation
Kick 1 space to the right of basic rotation
Kick 1 space to the left of basic rotation
In addition to these rules, there are some extra exceptions where certain kicks are not allowed.
The I-piece will never kick.
L, J, and T-pieces, from their 3-wide orientations, will not kick off their center column.
Center column rule
The center column rule prevents many unusual kicks which would otherwise be possible without the rule. Another side effect of the rule is that some rotations are not reversible, unlike with SRS.
L, J, and T-pieces use a 3x3 bounding box to hold the piece information, when referring to the center column, it means the center column of the bounding box. If any of these three pieces are rotated, an algorithm checks if the piece collides with the stack or playfield edges.
The algorithm for checking colliding blocks searches in the following pattern:
If the first block found in the search is a center column block (cells 2, 5, or 8), the rotation will fail. However, if the first block found isn't in the center column, and a kick is possible, then a kick is applied.
In the situations illustrated below if the block is occupied.
However, there are very similar situations where additional off-center blocks will enable a wall kick. In the situations illustrated below, the upper occupied blocks are off-center and enable the kick even in the presence of occupied blocks in the center column.
Clockwise rotation will successfully kick:
Counter-clockwise rotation will successfully kick:
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
This can be taken advantage of to rotate the J-piece over obstacles during 20G.
IRS counterclockwise
Move right
Rotate clockwise
Place piece
Kicks changed in Tetris with Cardcaptor Sakura Eternal Heart
In Tetris with Cardcaptor Sakura Eternal Heart, tetrominoes will only try to kick in one direction, based on what part of the block detects a collision first in this order:
Collisions with 1, 4, or 7 will try to kick the piece right, while 3, 6, or 9 will kick left. 2, 5, and 8 will still prevent kicks as mentioned above. Some examples:
This example will fail to rotate because its one kick isn't open:
I still doesn't kick.
Kicks added in Tetris The Grand Master 3 Terror-Instinct
In Terror-Instinct, the I-piece 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-piece floor kicks
The I-piece 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-piece floor kicks
The T-piece can escape from a hollow, up to two times.
Try to rotate
Basic rotation fails
Kick up
Rotating a T or I-piece after it has floor kicked will permanently set the lock delay for that piece 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-piece 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 piece will instantly lock down, preventing rotation from being processed at all.
The T-piece 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 pieces 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
For this reason it is recommended to build a well on the right side of the playfield, rather than the left. This bias is seen in other games, such as NES Tetris.
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.
block is occupied.
