Optical illusion: what do you see?
In this particular puzzle, some people see constantly rotating circles, but when those people pause to reset their vision, they can see the circles have not moved at all.
For others, they can start the circles rotating individually, by darting their focus around the canvas at the differing circles, triggering movement in different parts of the puzzle.
Of course, the circles are not moving at all but because of the way the patterns are aligned, the eye and brain are tricked into seeing movement on the page.
Give it a go and see what happens for you, and then share the puzzle with your friends to see if you can convince them their mind is playing tricks on them!
Puzzle credit: Robson