While trying to defend your planet, your friends were killed by space invaders! To avenge them, you have to go after the invaders and kill them. There are lots of low level invaders, plus bosses. When you defeat a boss, watch for the chance to earn bonus points! Look for hovering items. They are weapon upgrades, and they will help you kill more invaders more quickly. To steer, use the up and down keys on your keyboard. Use the Ctrl key to shoot. Watch your energy bar. If it gets empty, you lose a life. You only get three lives, so be careful!