There are lots of different levels and you need to hit various targets before the time runs out.Use LEFT and RIGHT ARROW KEYS to look around and locate your targets. Then click and drag THE MOUSE to set angle and power of your shot.
You've to help him shoot and hit other obstacles before the time runs out to proceed to the next level.
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: