I love this one. Which square is darker, A or B? Look at it for a bit, then come inside for the answer.
They’re both the same shade. Just trust me, you can load it into an photo editing program and see for yourself. There you go. It’s all smoke and mirrors. Relativity diversity kicking your ass again. That cylinder throws you off because it suggests a light source and casts a shadow of relatively different shades. If the light was coming from the opposite direction we would see the trick exposed.
Go have some more fun here. I love that Charlie Chaplin one.