Anaglyph 2D Depthview
You will need anaglyphic 3d glasses (a red-light-filter on the left side, a blue one on the right side) for this demonstration!
This is a fun mini project. I wondered how a flatlander (an inhabitant of a 2d world) would perceive his surroundings. We 3d creatures essentially see a 2d image of the world and in the same way probably a flatlander would also only see a 1d image of his surroundings. However, by having two optical sensors (aka eyes) one gaines the ability of depth view. You still cannot see the backside of the object you are looking at, but by looking at the small differences in the inputs of the two optical sensors you can at least make out how far something is away from you. This would probably also be possible in 2d for a flatlander and that is exactly what I showed in this demonstration.
(not working on most smartphones)