Puts cylinders in front of a mirror and reflection is squares. And vice-versa. <https://www.youtube.com/watch?v=oWfFco7K9v8> (1 min). And once you are befuddled and confused..... Ambiguous Cylinder Illusion // How it Works <https://www.youtube.com/watch?v=SKpOKXAVjGo> (2 min). BillK