In ORBTRUDER, you control a small killer robot ball that ricochets off walls and enemies. Gameplay is divided into a series of locations, each ending in a boss fight. Each location is procedurally generated anew each game session and is divided into rooms. The rooms have doors that open only after all enemies in front of them have been defeated.

Orbtruder features mini-quests and special events that can grant the player upgrades for their robot. The robot can run, jump, hover, choose its attack direction, and fire. Each enemy has weak points, and depending on the damage to these weak points, the robot will change its behavior. If the player dies, the game restarts. All upgrades are lost, but any achievements unlocked remain.