JUST REALIZED DEPT: ALL First person shooters are really Pac
  Man. The difference? You never lose your Power Pellets and can
  always eat the ghosts. [kill your enemies] at least until you
  run out of ammo or if they're stronger. Then you lose your Power
  Pellet ability and they can kill you.
  Shoot your enemy, eat your enemy, Get killed, get eaten, not
  much difference except the mess.