From back of box:
Get ready for Xenocide, Micro Revelations's New Science Fiction arcade game that is sure to take your breath away! Now you can get the fast-paced action and dynamic sound of the stand-up arcade games right in your own Apple IIgs. Only with the Apple IIgs' superb graphics and unparalleled sound could we have been able to create a product of such magnitude.
..
In Xenocide, an alien race has taken over research outposts on the three moons orbiting the planet of Talos IV. There have been no recent communications from any of these three outposts and thus we must assume the worst - there are no humans left alive. In order to halt the spreading of the alien race, you must destroy the three moons.
To accomplish this, however, you must travel across the surface terrain of the moons to collect ammunition remains from the former colonists. With any luck, you will find the entrance to the inside of the moon and be able to enter the underground caverns.
From there, you will need to collect miscellaneous items that will help you complete your mission. When you are prepared, you will enter the Bio-Labs at the heart of each moon and attempt to destroy them.
By placing the explosives that you have collected. The Bio-labs, once the top secret research centers for the scientists, have been taken over by the aliens so they, not too surprisingly, may conduct biological experiments of their own.
You MUST reach all of the labs in each moon and destroy them before it is too late.
Only one as brave as yourself could possibly carry out the mission of Xenocide!