Here's an optical illusion I discovered by accident on the cover of a copy of Sainsburys Magazine, of all things.
how to see it
First of all, click here to see the cover normally with a picture of a white frosted cake with a slice cut out of it. Nothing unusual here.
But turn the image upside-down, and look what you have - a single slice of dark chocolate cake! Do you see it?
Proof that Jamie Oliver isn't the only thing from Sainsbury's that messes with your eyes.