Leviathan takes place on isometric science-fiction landscapes where all enemies have to be destroyed. So the player mans a space ship, flies around the three levels (with the ability to turn around and change the flying height) and shoots everything he see. Besides flying enemies there are also defense stations on the ground to be dealt with. But while rocket ammo is unlimited, fuel has to be regularly refilled by landing besides a fuel pod. Three smart bombs which destroy everything on the screen help in tight situations. Every level runs on a time limit.