Pick up the photon gun and get ready. Use "W", "R", "S", "F" KEYS to control direction of shooting. You get 1 point per missile you destroy. You loose 1 point for hitting a grenadier. You loose 2 points for every missile that hits you. There are 10 levels.
Take this training session from four grenadiers to become a Trojan guard.
GameCanvas is a Canvas with additional capabilities; it provides methods for immediate painting and for examining the state of the device keys. These new methods make it possible to enclose all of a game's functionality in a single loop, under control of a single thread. To see why this is attractive, think about how you would implement a typical game using Canvas: