Zackman: The Pit

This game is a Dig Dug clone, the game play is identical to Atari's Dig Dug arcade game, with the exception of two things: 1- You can't attack the bad guy up and down, only left and right 2- The overall object is to grab a prize at the bottom of the screen, and then get back to your ship that dropped you off at the top of the screen. If you shoot all the bad guys, a new one will just appear somewhere.