Like many of its contemporaries in the less litigious 1980s, Mega-Apocalypse was a shooter heavily styled on an existing arcade cabinet, Atari's Mad Planets. The direct sequel to Crazy Comets, an earlier moment of "inspiration", the aim of Mega-Apocalypse is simple - destroy as many planetary bodies as possible before the inevitable demise of your spacecraft.
The player must contend with rapidly expanding planets which spawn at regular intervals. Smaller bodies are easy to destroy, but if a player allows a planet grow to full size, it becomes aggressive and much harder to destroy. Consequently, a key mechanic of the game is swift destruction of pint-sized planets to avoid being overrun with their larger and deadlier counterparts.
Any collision with an enemy results in the loss of a ship, although more lives are available during gameplay. Numerous power-ups can be collected for more expedient destruction, while score bonuses are awarded for saving stranded spacemen.
Though the single-screen graphics were rudimentary for the time, the Commodore 64 version of Mega-Apocalypse received many plaudits for its audio on account of its Rob Hubbard soundtrack and sampled speech.