The object of Geometry Fighter is to survive as long as possible and score as many points as possible by destroying an ever-increasing swarm of enemies. The game takes place on a rectangular playfield and the player controls an dagger-shaped "ship" that can move in any direction using swipe controls, and fires automatically at enemies. The player can also earn a limited number of bombs that can be detonated and destroy massive number of enemies. As the game progresses, the player can unlock new weapons at set score increments, and the primary weapon changes be changed at will by picking up powerups. Also, enemies spawn in progressively larger quantities and at greater frequency as the game progresses. If an enemy touches the player's ship, the ship explodes and a life is lost. The game is over when the player runs out of lives.