A Tribute to the Half Life 2 mod with the same name. Threw it together quite fast so it lacks a few things I may or may not fix :p
You are either a survivor or the Zombie Master who controls the hordes of zombies and traps on the map trying to prevent the survivors from escaping by completing the objectives.
Feel free to modify the objectives, etc while keeping the mode and giving some credit to me. Would be great to see more Zombie Master maps, since it's the unique objectives and traps that make it interesting.