This Is Your Brain, On Light
Lest anyone doubt the ability of lighting to manipulate our minds, here's a quick little illusion to scramble your brain. I read the full explanation on the YouTube page (you'll have to click 'show more' under the video there) and I think I understand it. Maybe.
But my brain is still a little scrambled by the fact that what looks like a shadow in the checkerboard isn't actually a shadow. It's a tone.
[BrussPup via Giz]