Stare at this cube for awhile. The blue side of the cube will appear to be either on the inside or outside of the cube. It’s either the closest side of the cube or the farthest away. It’s tough for our minds to perceive this optical illusion both ways, so you’ll see it switch back and forth the more you stare at it.
Another way to look at it is this: At first, the blue wall appears to be on the back side of the cube, with the yellow sides on the right and bottom, coming out toward you from the blue. Then, as it switches in our minds, the blue side is closest to you, with the yellow sides now on the outside and also very close to you, but they’re pointing away.
Like we said, the more you stare at this illusion, the more you tend to appreciate it because it will just keep doing that! Cubes that do this are called a “Necker Cube” and you’ll find them throughout the site. It’s perhaps the easiest optical illusion to draw as well, so try it out, next time you’re taking notes… jot one down, and shade in a couple areas of the cube, and who knows what you’ll come up with!