ARS

The ARS rotation or Arika Rotation System 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 TGM (Tetris the Grand Master).

Games using ARS 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 ARS rules and SRS rules.

Basic rotation
ARS'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.

Wall kicks
ARS 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 XTet.png marked block is occupied.


 * However, [[File:Bin6.png]][[File:Bin4.png]][[File:Bin4.png]] will rotate to [[File:Bin8.png]][[File:Bin14.png]][[File:Bin0.png]] and [[File:Bin4.png]][[File:Bin4.png]][[File:Bin6.png]] to [[File:Bin0.png]][[File:Bin14.png]]Bin8.png]] in the situations illustrated below if both the [[File:XTet.png marked blocks are occupied.

I tetromino's wall kicks
In TGM3, the I tetromino makes use of a wall kick.

This can be done in three ways:

I tetromino's floor kicks (TGM3)
The I tetromino can kick the floor.

Notes:
 * The floor kick can be performed only once per tetromino.
 * The tetromino cannot kick the floor in mid-air.

There are 2 different types of floor kicks.

T tetromino's floor kicks (TGM3)
The T tetromino can escape from a hollow. Note that this is not a wall kick in SRS.

Notes:
 * This action can be performed only twice per tetromino. See below.

Rotating a T or I tetromino after it has floorkicked 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 floorkick 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 ARS, 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.

Note that the I has 1 rotation axis;

I piece's rotation axis

This case does not apply to the I 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: J does not... ...unless there is another block to force a kick to the left.

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 ARS rotation. Normal ARS features Sonic Lock (locking hard drop) and non-locking soft drop. ARS2 had Firm Drop (non-locking hard drop) and soft drop (locking).