OK, rough sketching of the zombie rules, I have all the standard RPG rules already, thoguhts ppl...
OKAY, now for the zombie rules
We are going for the classic night, dawn and day of the dead zombies, meaning they are slow, super-strong and lurve brains, able to smell them from a distance etc, and feel no pain(for now).
Upon being bitten, 24 hours will see them turned into a zombie, HOWEVER if severely bitten as in a multitude of bites, the change can be quicker.
As with Romero, the recently deceased will come back to life as zombies
If you are bit in the arm, you have approx five minutes to sever the offending article of flesh and burn the wound to stop the spreading of infection.
The evolution of the Zombies will be something controlled by the zombie master, as to keep things cohesive etc
None of the characters know anything to do with why from the start, unless pre-arranged with a GM.
To kill a zombie, you have to sever its head(which will stop it being anything more than just a twitching head), shoot it in the head or pierce its brain with some other object etc. Obviously dissolving its tissue in acid etc will also make it cease to be etc. But as we all know, cutting off limbs and shooting it in the stomach etc does jack!