I'm going to be doing free association here and try to come up with many random details if I can. I remember playing an old game on DOS or Windows 3.1 and it was a shooter from a top down perspective, like the kind you see often on Flash game websites these days. You'd go from room to room, and kill all enemies in each room, and the rooms were separated by gates. The enemies were aliens, swarming types and if I remember correctly, there were many spaceships too. You shot at them using a repeating cannon weapon as your default. You could eventually gain other weapons (such as a plasma weapon) but the rest of the weapons had limited ammo and you'd default back to the unlimited cannon weapon if you ran out. At the end of each level, you'd face a gigantic boss, usually a spaceship or tank of some kind. I distinctively remember the second level boss being a train that would shoot at you using the plasma weapon I described. It had mines on that boss level. If it helps, the last boss initially attacked you with a swarm of fast moving jets that you had to avoid or die, and it itself was a mothership-ish boss. The game was set in an alien headquarters of some kind, with gray walls and electronic doors. After defeating the last boss, you see the alien headquarters exploding deliciously, in the middle of what seems to be a barren desert area. I know this is a stretch, but I was hoping to find out the title of this game. I've searched MobyGames, Gamefaqs, wikipedia and more, but I haven't nailed it down yet. I'll continue searching, and I'll be grateful for your assistance.