Aliens have infested Earth, and are spreading a deadly virus throughout the planet. Needless to say, they must be stopped, and fast. The time pressure (your score upon completing a level is based on the uninfected percentage of the land) is only one difficult aspect of this shooter.
Viewed in remote 3D with a patchwork-quilt type ground effect, with trees sticking out and full gravity. Controlling your spaceship involves balancing the direction and height as well as thrusting to the right speed. A scanner tells you where the aliens are.