Gameplay is rather simple. You are the VacFighter on the screen, you can move up, down and back and forth (default - arrows). Almost everything coming at you from the top of the screen is hostile!
Press the fire air weapon key to release weapons that will deal with airborne enemies. This key can be held down to power-up the weapon, emitting a stream of destruction on release. Be careful not to overload it though!
Press the fire ground weapon key to release plasma bombs against ground enemies and installations. Line up your foe in the crosshairs, wait until the crosshairs glow red, then fire and forget! This weapon automatically increases in power as you progress in your mission.
Additional Air-to-Air weapons become available throughout your mission. Press the change air weapon key to cycle through available weapons. To succeed in your mission you will need to master the art of changing weapons quickly and selecting the appropriate weapon for the target.
Collect bonuses and coins as they appear. As the war for Deimos progresses, the research & development team will develop new and devestating upgrades to your weapons systems.
If you want to see what the keys are assigned to, before you start the game, select the Preference option. This will show you a screen that has a button called Set Controls. Select that button to see what is assigned to what keys and to change the assignment to whatever you want.