Written by Greg Christensen, Caverns of Mars is a simple but attractive vertical scroller shoot-em-up in the style of River Raid. Your spacecraft flies through successive levels shooting at stationary or mobile targets. Your fuel is always running out, and blowing up fuel depots and spaceships replenishes your stores. There are four levels of difficulty which determine the number of levels you have to fly through to win the game. Caverns of Mars was distributed by the Atari Program Exchange (APX), a third-party mail-order software group. Due to its popularity, it was later distributed by Atari proper. (User summary)