Stare at the dot in the center as this animated gif plays on, and after 10 to 30 seconds, the blank shapes, whenever they appear, are filled in by a "ghostly" color. That's a very familiar illusion, but there are two strange thngs going on here: (1) The colored images are not one uniform color, but the afterimages are. (2) The color of the afterimage (either pale red pale or blue-green) depends on the shape of the blank figure! If it's a star (that is, if one of the four points is pointing straight up), the afterimage will look reddish, because reddish is the "opponent color" or complementary color of the bluegreenish in the colored figure of the same shape. If the same shape is rotated sideways 45 degrees, the afterimage is bluegreenish, because the originally-seen figure of that shape was colored reddish. What's more, if you continually view one, and then the other, as in the series above, the perceived after image immediately changes from one color to the other! This remarkable illusion should be credited to Professors Rob van Lier & Mark Vergeer.

Another variant of a familiar illusion; and unlike most versions, it is very strong. The two red circles look quite different in size, an illusion apparently created entirely by the surrounding grey "tire" differing in size. Does the "thick" tire seem closer, therefore the red circle larger? No, in fact the red circle in that case appears smaller! Why??? Of course, both red circles are identical.