Click the green flag to start. Use your mouse to move up and down. Hold space to use your machine gun. Click the UFOs to shoot missiles at them. Type the S key to use an energy shield. Each shield lasts 5 seconds. You can't get hit again unless 1.5 seconds have passed. When you defeat a UFO there is a chance that it will drop a missile or energy shield that you will automatically pick up.
Thanks to Lockheed Martin for the F-16. Please Heart and star.
