In each level of the game, the player must prevent waves of enemy
space ships, launched from
motherships on the edges of the screen, from reaching the player's base in the middle of the screen. To accomplish this, the player must deploy various types of armed
satellites, which can be placed in predefined slots on different
orbits around the base. The player can also rotate an orbit to move all satellites in it to a new position. Destroying all enemies efficiently usually requires the player to reposition their existing satellites so that they can reach new waves of enemies, which can take different paths to the base. In addition to armed satellites, the player can also deploy unarmed satellites, which can, among other things, generate money for buying more satellites, repair other satellites or slow down nearby enemies. == Plot ==