Faces everywhere
Hollow-face illusion
As the mask turns, which way does its hollow back face?
It still looks like a face pushing toward you, and seems to turn the wrong way.
Why? You have seen thousands of faces that stick out and none that go in, so your brain refuses to see a hollow face.
Picture: cmglee, hong227, CC BY-SA 4.0 · Wikipedia(opens in a new tab)