Star Gunner is a shooter game with a futuristic setting. The story goes that the people of Zile, the inhabitants of the Andromeda Galaxy, are becoming restless. They are beginning to covet the resources of another planet called Ytima, and are secretly preparing to attack the people of Ytima so they can claim the planet as their own. The people of Ytima learns about this plot and prepare to defend themselves by training an elite squad of soldiers, called Stargunners.
The mission of the Stargunners is to attack the planet of Zile first. They are to destroy the three strongholds of their enemy planet, where the war fleet of the Zilions are waiting for the launch order. By crippling the enemy strongholds, the people of Ytima will have an advantage. The Stargunners must accomplish their mission as secretly and as swiftly as possible and use the element of surprise in their attack.
Players assume the role of a Stargunner and aim to destroy the warships of Zile. Destroying the enemy warships lets the players earn credits and power-ups. This game has three levels of difficulty and 33 stages that are set in different arenas, such as terrestrial, stellar, and aquatic. At the end of each major stage is a boss that must be beaten in order for players to advance to the next stage.