Survive for as many days as possible, while converting zombies into a human or vice versa.
As a human it is your goal to shoot as many zombies is possible with an experimental reversal drug that will make them human again.
If you are unlucky enough to be infected by zombies yourself, you turn into one. Once you are a zombie, you have a new objective - infect infect as many human as possible so that they are converted into zombies.
* Operating systems Windows 7, Windows 2003, Windows Me, Windows 98, Windows 95, Windows 2000, Windows Vista, Windows XP