some people dont notice but you are a unit and can move with wsad and leave the castle and can heal yourself just like any other unit but you cant pick up the flag
basic tips :
-in early levels only make headshots as there the only ones that count
-try to make your first new weapon something automatic
-keep a long range high damage weapon and an automatic weapon on you at all times
-use the Springfield / hunting rifle at first to thin undead numbers then when they get close use a
low recoil automatic weapon for easy headshots to mop up the rest
-health comes before anything else, always use time to heal first and keep your health at max or close to max AT ALL TIMES.
-always keep at least 1 survivor shooting with you at all times to watch your back
-take every opportunity to try to get the grenade launcher
-when you get the grenade launcher simply mash the mouse button and aim at groups of zombies for extremely simple wins
-don't put any survivors you want on a search party
sincerely - a guy who got through my entire first run without a single death.
please rate up to keep alive
hope it helps