Your flashlight is flickering, your friends are gone, and you're down to the final mag of ammo. Stepping out onto the roof of the warehouse everything goes eerily silent. You whip the barrel of your M4 assault rifle from side to side, casting dim light on every corner of the rooftop, and then you see them; two dozen creatures in a dead sprint to your position. Do you run, or stand tough?
This is Left 4 Dead.