An optical illusion is when you look at one thing but your brain perceives it diff erently than it actually is. By understanding the way the human eye distinguishes

the distance of objects we can trick the player of our game into thinking the two-dimensional game they are playing is actually a three-dimensional game. In the world of game design this technique is called 2.5D. 2.5D uses two-dimensional images in such a way that they create the illusion they are moving in a threedimensional space. Before computer technology allowed designers to create fully three-dimensional games, 2.5D was a common technique used to simulate a 3D environment. Before starting, however, we must have a basic understanding of how we perceive objects in the world. Figure 6.1 simulates two objects in a 3D space.