Defend your planet against a foreign invasion. When you start, you have to choose what you want to use to play. You can either use your mouse to guide the spaceship and click to fire,or you can use the direction keys on your keyboard to steer. With keyboard mode, you have to push the shift button to shoot. In both modes, push the space bar to use Nova Discharge. As you move around on the screen, shoot at oncoming enemy forces to kill them before they kill you. Use Nova Discharge when there are too many enemies for you to clear by yourself.