Do you know some really good illusions ? Not obligatory with optic, it can be with sound or both.
It can be a video, a picture or everything you want.
I watched a show yesterday where they explain how our brain works and why he is confused by illusions.
It is very interesting I like it too.
(It is a picture, suggest look at it on mobile cause you can see different when you turn it)
The trapezoidal window of Adelbert Ames
The one that I prefer is the chessboard of Adelson.
Hard to believe but the cases A and B have the same color. You can move the grey case next to it the chessboard to be sure.