Berzerk

You have been sent into a building infested with robots, and must do your best to clear it out. Each room has a number of walls through the middle, which restricts your movement. There will be a number of bad guys in the room - on early screens they may be immobile and not shoot at you, but after a few levels, they become capable of shooting in multiple directions. You can shoot at them in 8 directions, but can't shoot diagonally while moving. There are gaps at the side of each room, through which you exit, before or after clearing the room (there is a bonus for clearance). You get an extra life every 2000 points.