OK, if you've got nothing else to do for one minute, let me mess with your head.
Below, you will see two circles composed of parallelograms. There's a dot in the middle of the image. Focus on the dot. Move your head in, then move it out.
The circles seem to rotate.
(Of course, they don't really rotate; if you focus on a single parallelogram, you can move your head in and out all day and that sucker won't move at all.)
Something curious is going on.