In Mad Planets, the player takes control of a spaceship and must attempt to destroy a series of Earth-like planets which emerge from the center of the screen and rapidly move towards the player's ship - increasing in size as they do so. Destroying all of the planets in a round before the they reach their full scale will see the player awarded with bonus points. Fully-grown planets are orbited by a number of small moons, which, if destroyed, cause the planet to go 'mad' - turning red and making a beeline for the player's ship. The game also includes bonus rounds in which stranded astronauts can be rescued for additional points.