Canabalt is an addictive game where you must run for your life along a series of rooftops, using one simple button to leap over obstacles, jump from one roof to the next, all to gain enough speed and acceleration to outrun your doom. It is exceptionally done thanks to little presentation touches like the way you leap through panes of glass, scatter flocks of pigeons in your path, and run to a soundtrack that captures the sense of both alarm and speed. Canabalt is free online, but also available for as an app for those with an iPhones/iPod Touch.