Twisting spiral

Twisting spiral produces different illusions depending on what direction you spin it.

If you spin the spiral in one direction, the pattern grows outwards. Rings appear from nowhere in the centre of the disk and disappear from its outer edge, into thin air. Spin the disk in the other direction, and you see spiral rings that fall inwards. They disappear in the centre as if falling into a hole – new rings are added continuously from the outer edge.