Move your mouse to steer your ship. The ship will turn in the direction of the mousepointer. Keep your pointer close to the centre for a small turn, and close to the edge for a larger turn. When the enemy ship is in the centre of your viewfinder, click anywhere (or press the space bar) to fire your weapons. Click on the speaker in the bottom left-hand corner to turn off the audio clips. The enemy ships will try to escape. If 10 manage to escape then the game will end.
Credit for the design of this game goes to Bob Bishop who wrote a version back in 1977 for the Apple ][. He describes it as the second ever hi-res game for the Apple. http://bob-bishop.awardspace.com This is the Scratch 2 version of the game which uses cloning to create a selection of stars at runtime.
