Puyo Puyo Tetris movement intricacies

Intra-frame processing order
In Puyo Puyo Tetris, inputs are handled in the order of:
 * DAS
 * Hold
 * Rotation
 * Movement (processed, but not set)
 * Gravity (includes soft drop)
 * Hard drop
 * Movement/Auto-Shift (set)

Due to an oversight in the code, it isn't possible to move and Hard drop on the same frame, as it processes the movement, but before it can set the position of your current piece, it processes hard drop. This also applies to movement from Auto-Shift.

Using Cheat Engine, it is possible to modify what inputs the game processes on a given frame, and to see what happens if you do more than one action in a single frame with no room for human error:
 * Left + right simultaneously - no shift
 * Left + harddrop - piece hard drops, no shift
 * Rotate + harddrop - piece rotates then hard drops
 * Left Rotate + Right Rotate - no rotate
 * Rotate + move - piece rotates then moves
 * Hold left while right DAS charged - piece shifts left, piece stops DASing right.
 * Hold right while left DAS charged - piece shifts right, piece stops DASing left.

Entry Delay / ARE

 * DAS can be charged during Entry Delay
 * Hard drop inputs during Entry Delay are ignored
 * Tapping Left/Right inputs during Entry Delay are ignored (however, the keyheld event is processed - DAS can be charged)
 * Hold inputs during Entry Delay ignored
 * Rotation inputs during Entry Delay are mostly ignored

Puyo Puyo Tetris does have a form of IRS that can be activated by pressing a rotate button ~3 frames before entry (exact timing unknown), but it isn't "true" IRS as the piece still spawns in the basic orientation. Activating IRS in Puyo Puyo Tetris only makes the game rotate on the first frame you would be able to normally, offering no speed advantage in any case.

DAS Double-Charging
DAS is charged on two separate counters. It is possible to charge both DAS counters at once.

E.g.
 * DAS first piece to right wall. Drop
 * Hold left, do not release right.
 * Das second piece to left wall. Drop. (Left and Right DAS are both charged)
 * Release left key. Piece will go right with DAS Charged.

Input mixing
Puyo Puyo Tetris offers a variety of presets for control configuration. In most presets, some actions have some form of alternate button or input (e.g., the default preset allows pieces to be moved by either the d-pad or analog stick).

The game engine handles this many-to-one relationship between inputs and actions with what one could consider just one "virtual input" per action. If an input for an action is already held, pressing the alternate input will not trigger that action again. (e.g., simultaneously pressing two movement/rotation buttons will not trigger a double tap shift or 180 rotation). Moreover, if both inputs for an action are held, releasing one of them will not do anything special; the game considers the action to have been continuously held. (reference: Kitaru) This means that from an input perspective, no new quirks are possible compared to having only physical key per logical input.