Great game that scratched the zombies itch

I bought this at a friends recommendation maybe around 2011-2012. I had swapped from console to PC around then, didn’t have a great one and I also didn’t want to rebuy a call of duty game with my limited funds. Got this on the winter sale that year and man it was so fun. I can still see the snowy update for the maps and the little skins they put on some characters. Fun progression albeit a little slow, was rewarding to know your character and build and improve, but did get a little monotonous once you figured things out. I can’t remember specifically but if I’m recalling correctly the hardest difficulty was pretty dang hard. Overall it was a really really good purchase that got a lot of play with friends.