Parker Brothers released contemporary ports for the Atari 2600, Atari 5200, Atari 8-bit computers, ColecoVision, and Commodore 64. A version for the ZX Spectrum was coded but never released.
The entire solar system is being attacked by the vicious Gyrusians, and it's up to you to save the day! You will need to fly your spaceship to each of the nine planets and then clear three stages of enemies to rid that planet of the Gyrusians. You start the game with a single cannon, but can gain a double cannon after shooting a power up satellite. After clearing each planet, there is another bonus stage where additional weapons and bonus points can be collected.