Thought to post something “light” for the weekend 
here you will find a very cool web site with many opticall illusions and visual phenomenons.
These pages demonstrate visual phenomena and »optical illusions« or »visual illusions«. The latter is more appropriate, because most effects have their basis in the visual pathway, not in the optics of the eye. I selected these based on relative novelty and interactivity. When I find the time I will expand the explanations , to the degree that these phenomena are really understood; any nice and thoughtful comment welcome.
