This one is a concave/convex kind of shift. The way to switch your perspective from one to the other is to concentrate on her spinning foot and its shadow just below.
Do these circles of squares intersect? Where?
This one just seems obvious after the first time. Try staring at the left side and pay attention to the shading.
This one is crazy. The “green” and the “blue” are the same color. You can kind of see it on the edges of the outer spirals, or by zooming into to the individual pixels.
Tags: optical illusions