The mind is a curious thing. It makes inferences from what you're viewing with your eyes, meaning that if manipulated just right, it's easy for illusions to skew your perception. The effect in the video below from YouTube channel 'Brusspup' is called an anamorphic illusion. It uses perspective to challenge the viewer's sense of perception. It's particularly effective on film, because a camera has no depth perception. In this video, the illusions look totally mind-bending, yet if you were seeing them in person, it would be obvious which items were 2D and which were 3D. If you want to mess with your mind, this is the perfect way to do it. Take a look!