You are in command of the only defences on the Red Planet. You must shoot down the invading Zargons which soar over the barren terrain from your left on regular sorties. Those that you miss will now come from the right, but don't forget that another ship will be coming from the left at the same time. As they fly over they drop shells onto the city below. Activate the forcefield to deflect their missiles, but exercise caution as energy is limited. Given time the energy banks will recharge fully. There are three types of enemy craft altogether: Bombers, Flappers and Fighters, each with a different flight pattern. An extra city is given for every 10,000 points scored.