The original one. That's the only "shoot-em-up" game I've ever played through. I don't need the stress. I got nightmares one night about the "sewage plant" level.

The game was relatively fixed in nature. If there were three bad guys behind a door, there would be three there no matter how often you played. This led to a kind of "Groundhog Day" tactic. On your tenth or eleventh failure to get through a level, you could use your experience to develop tricks. Like if you knew ten guys were coming out a door when you opened it, you could slap a load of land mines in front of the door before you opened it and ran like a little girl.