Fantastic Voyage(1982)

The game is based on the 1966 movie of the same name. The player controls a miniaturized submarine which is injected into the bloodstream of a gravely ill person. Your task is to destroy blood clots which are clogging the arteries in order to keep the patient alive. If you fail to do so or crash your submarine the game is over. While voyaging throughh the body you have to destroy other enemies such as bacteria. However, you should not destroy the blood cells lest the patient dies.