Fading Color Dots
Stare directly at the cross in the center of this demonstration until you see a green dot appear under each fuzzy purple dot.
The green dot is an afterimage. It only exists in your mind’s eye. This program does not make them.
Keep staring at the cross until the fuzzy dots begin to fade. If you look long enough they will disappear completely. You are now left with a single afterimage dot moving around the circle.
The four fuzzy color choices will each generate a different afterimage color. Can you guess what they are?