The objective of this game is to kill all flies. This is done with a fly swapper, controlled with the mouse cursor. Each time the fly swapper is next to a fly, the fly is killed and becomes a dead, undestructable object. The fly swapper can not move through a dead fly, neither can living flies. Each level has preset walls and bonuses. A bonus can mean that instead of a fly swapper, the user controls a spray so that dead flies disappear instead of becoming undestructable objects.