As Tal, your job is to single-handedly clear out the aliens who have invaded a desolate and destroyed post-nuclear earth. To have any chance of this, he must locate a sacred suit of armor. Not only will this protect him from radiation, and allow him to withstand some enemy contact, it also heals him, and enables him to float.
This means that the game has two distinct styles, with your character limited to jumping, and with only rocks (located around the screens) to throw. Once he finds the suit he can fly around the ledges, shoot the inbuilt Pulsar beam, and survive within the volcanic hideout the aliens have based themselves. You will need to recharge the suit at times, and also take it off to pass through tight caverns.