Commander Keen in Goodbye, Galaxy is a two-part episodic side-scrolling platform video game. It consists of the fifth and sixth episodes of the Commander Keen series. The game follows the titular Commander Keen, an eight-year-old child genius, as he first journeys through the Shadowlands to rescue the Gnosticenes so they may ask the Oracle how the Shikadi plan to destroy the galaxy, and then through the Shikadi's Armageddon Machine to stop them. The two episodes feature Keen running, jumping, and shooting through various levels while opposed by aliens, robots, and other hazards.