Star Legion is a sci-fi shooter. It takes place on a distant planet which is the only place where the valuable spice grows. Corporations set up colonies to harvest the spice, but the planet is inhabited by hostile combat robots. The player is the member of the Star Legion which protects the colony structures and vehicles from the robots.
The player flies around in his ship, seen from a third-person perspective. His task is to destroy combat robots which try to damage the colony buildings and harvester vehicles. Some of the robots can also damage the player's ship. If the player's ship or any of the structures is destroyed, the mission is failed and must be restarted. The player begins with a laser cannon, but different kinds of weapons can be purchased from the trader who occasionally arrives to the planet. Money is acquired through successful spice harvests (the harvesters gather spice automatically) and gathering pickups that sometimes fall out of destroyed robots.