A shoot-em-up where you fight devil-like creatures while trying to save a person's body. In this shooter, you pilot a microscopic ship through a human body. As you cruise through the bloodstream, you shoot down little devils that throw arrows at you - only 2 bullets can be onscreen at a time. If you move forward, the screen will scroll faster. This is necessary because you have a time limit/oxygen bar that will cost you one life if it runs out. You can pick up oxygen capsules to refill the timer. After this level, you defeat a bacterium inside the heart. After a second bloodstream segment where you shoot small dividing blobs, you destroy a virus inside the stomach. Then you fly through a third bloodstream level with hard-to-shoot bugs. Finally, you go through a maze inside the eyeball. The game appears to loop after this.