You are Deuce Darkstar on a secret, daring, foolhearty mission to infiltrate the Domain of Shmup and stop the Alien Downpour they are preparing to rain down upon all you know and love. You know it's a suicide mission, but you eat suicide missions for breakfast and you're mighty hungry.

Created to celebrate the 40th birthday of the Apple II line, Alien Downpour pays tribute to old-school shoot-'em-up action. There are sectors upon sectors of hostile space baddies to vanquish, bosses to defeat, and obstacle-course sections to test the player's agility - complete with references to fondly-remembered past games (and to Apple II history).