Galaxian is a classic shoot 'em up game where you play as a defender against an alien invasion. The objective is to destroy hordes of enemies at the top of the screen while avoiding obstacles and waves of bombers. With different types of aliens, each with varying point values, the challenge increases as you progress through levels.
The gameplay involves moving left and right along the bottom of the screen to target specific aliens, shooting bullets up towards them to destroy them. The aliens are categorized into four types: Drones, Emissaries, Hornets, and Commanders, with higher-scoring targets at the top of the screen. As you clear waves, new ones are generated, requiring quick reflexes and strategic thinking.