The story follows a ship sent to protect humanity from an alien invasion. The player's goal is to defend the Earth against waves of attacking forces, including Bombers, Pods, Swarmers, Baiters, and Landers.
Gameplay involves navigating through space, using smart bombs and hyperspace to fight against enemy ships. The player must also rescue humanoids from falling off the screen or being transformed into deadly mutants. With each wave of enemies that reach the planet, the chances of failure increase, making the game increasingly challenging.