User:Nightmareci/SRS

True Rotations

DeHackEd/Mufunyo!

Offsets

I

0°	(+0, +0)	(-1, +0)	(+2, +0)	(-1, +0)	(+2, +0)
90°	(-1, +0)	(+0, +0)	(+0, +0)	(+0, +1)	(+0, -2)
180°	(-1, +1)	(+1, +1)	(-2, +1)	(+1, +0)	(-2, +0)
270°	(+0, +1)	(+0, +1)	(+0, +1)	(+0, -1)	(+0, +2)

J, L, S, T and Z

0°	(+0, +0)	(+0, +0)	(+0, +0)	(+0, +0)	(+0, +0)
90°	(+0, +0)	(+1, +0)	(+1, -1)	(+0, +2)	(+1, +2)
180°	(+0, +0)	(+0, +0)	(+0, +0)	(+0, +0)	(+0, +0)
270°	(+0, +0)	(-1, +0)	(-1, -1)	(+0, +2)	(-1, +2)

O

0°	(+0, +0)
90°	(+0, -1)
180°	(-1, -1)
270°	(-1, +0)

Explanation of Offsets

Upon pressing a rotation input, clockwise or counterclockwise, there is orientation-start (the orientation before the rotation input is sent) and orientation-end (the orientation that will possibly be changed to). True rotation is performed from orientation-start to orientation-end, even if intersection occurs. Next, the first offset pair is attempted; given (a, b) as the first offset for orientation-start and (c, d) as the offset for orientation-end, the number of columns the offset attempt goes rightward is a-c when a-c is positive and leftward if a-c is negative, and the number of rows upward is b-d if b-d is positive and downward if b-d is negative. If applying the first pair of offsets results in some intersection with the field or walls, then the next offset pair is tried, and so on, until an offset pair succeeds; if none succeed, then no change in state will have occurred.

Examples

This is an example of I rotating from 0° to 90°, which is one clockwise rotation input in-game, with the true rotation center marked all the way through:

Start.

0° -> 90°, true rotation.

    Subtract
  |----------|----------|
  v          v          v
(+0, +0) - (-1, +0) => +1 horizontal offset, +0 vertical offset. Success.
      ^          ^                            ^
      |----------|----------------------------|
        Subtract

End.