I bet this will give you a headache.

Look at this illusion. The grey in square A is the same shade as in square B, your brain just refuses to belive it. If you don't belive me, save it and copy the colors with paint, scrible between the two squares, and see for yourself, about 20 of us did so over at another site just to prove it to ourselves.

Enjoy your headache.

Enjoy your headache.