Eternal is a science fiction side-scrolling platform game on time. Controlling a small robot the player must reach the exit gate before the time runs out, avoiding hostile units and traps such as stalactites, hooks or water reservoirs. The robot has an limited ammo. Contact with hostile unit lowers energy level, contact with a trap takes a life. Each of 27 levels consists of a limited number of diamonds. Collecting 50 diamonds adds one life.