If you’ve got a few minutes to spend boggling your mind, try visiting this eChalk optical illusion site to marvel at the weirdness of your brain and optical perception. The absolutely bizarre thing is, even when you know that you’re being fooled, it still happens. And it’s no good explaining it to me, I still can’t get my mind to work it out properly. The ballerina and the rotating mask ones in particular are both incredibly frustrating and it’s just not fair! Madness.