The Earth is being invaded from space by the Epsilon Empire and have already landed. To thwart the invasion, a humanoid robot is sent out to blast the aliens away.
Cosmic Epsilon is an action-adventure game that features 3D effects using the Famicom 3D System. Players alternate levels with their robot character in either flight mode or in humanoid mode. There are a variety of settings for each level.
Gameplay involves moving around the screen area, attacking enemies coming from the background into the foreground. The player can use homing missiles or the default Vulcan beam to destroy them. The Vulcan Beam can be charged up for extra damage. Powerups can be collected from defeated enemies.