This trick's been around for a long time as an image, but this YouTube video seems to bring the whole illusion to life.
The mind-blowing shade experiment is based off this template, which almost seems too simple to work. But if you watch the video below, we dare your mind not to be blown.
According to the YouTube posting the initial idea was brought to light by MIT professor Edward H. Adelson. The post's description also attempts to further explain the illusion, though it's still hard to believe, even when you know what's going on.
We think this illusion's a bit more believable than this one, whether or not you think it's real is your decision to make.