Space Gun is an action-packed rail shooter experienced from a first-person perspective. You must fight hostile aliens that have invaded a research ship and taken the crew hostage. Some monsters can only be defeated by first shooting off their limbs, while others attack from the air with mechanical cannons. At the same time, the player must rescue innocent hostages – but beware, as some may suddenly mutate into dangerous creatures.

In addition to the rapid-fire standard weapon, there are four alternatives: flamethrower, grenade launcher, freeze bomb, and blade bomb, all requiring collected ammunition. The game offers six to seven levels divided into sections, each ending with a boss fight. Along the way, the player can choose different routes through the ship, while short cutscenes advance the story. Strategy is crucial, as using the pedals to move backward buys more time but risks losing valuable level time.