I am quite new to this game so bare with me. I have started an online campaign with a friend. At the end of each level it gives the amount of zombies each of us has killed. What I don't get is how come you can select what ever level you want to play? Why aren't tehy unlockable as you progress through the game? I take it there isn't a way to view total number of zombies killed in the overall campaign. Or have I just set the game up wrong? Any help on this would be very much appreciated .