A number of elements are involved with game design: characters both endearing and despiteful, in-depth detailed environments, audio—both sound effects and musical score—and a real challenge. Note that neither realism nor winning are components necessary to a great game. Since we are concerned here with interactivity and shader languages, we will look at how lighting, implemented in shader languages, can be used in game design.

Several years ago, before the introduction of the first iPhone, 3D graphics applications were already being written for mobile phones that had 3D graphics hardware. One of the first games was A Teenager's Bedroom. Its goal was to find your keys, wallet, feed the fish in the tank, and any other critical elements of a teenager's day. In the bedroom, every object could be thrown while looking for your keys and wallet, including couches, tables, the bed, pizza boxes, a case of beer, or a bag of potato chips. The fun was actually destroying the room, not...