Still pictures that move
Sliding checks
Look around the picture. Do the rows move? Then look at it from far away: are the rows straight?
Up close the rows seem to slide sideways; from far away they seem to slope. Both are still and straight.
Why? Two illusions in one. The squares shade from dark to light, which your eyes take for movement. Seen small, the offset rows become a café wall illusion, and the lines between them seem to tilt.
Picture: Drawn by Science Playground, after Mardeg · Wikipedia(opens in a new tab)