Turns the picture. rotation is in degrees.
The one subtlety is aspect ratio. On a widescreen canvas, one step sideways and one step up are not the same physical distance, so rotating without accounting for that turns a square into a leaning parallelogram. The effect squares the coordinates up before turning them and puts them back afterwards, which is why things stay the shape they were.
speed spins it continuously rather than rocking back and forth, and a whole number gives a whole number of turns per loop, so it comes back exactly to where it started.
wrap decides what fills the corners that turning exposes. mirror is the safe default because the reflected content meets the original edge to edge with no visible join; repeat tiles, and clamp smears the edge pixels outward.