COD Zombies Rip-Off Launches On Steam Completely For Free

I'm a little surprised that Call of Duty Zombies didn't inspire a wave of indie games in the same way that Left 4 Dead did. Sure, there are a couple of gems on the Steam store, but they're hardly as prolific. Then came a little free-to-play game called Nazi Zombies last week, and while it's an unashamed rip-off down to the Ray Gun, M1911 starting pistol, mystery box, power-ups, perk machines, and Pack-a-Punch (sorry, the bless-your-guns ATM), it's pretty damn good?