Stare at the black dot...
Move your head back and forth toward the screen and notice the rings move in opposite directions!
Your brain is trying to "fix" information being seen in your peripheral vision..
Your brain is fooled by the repeating shapes being shaded to be either up or down
depending on your perception. The shapes in the smaller ring conflict with the shapes
an shadowing in the larger ring... notice that when you are further back there is less effect
than when you are close up!