The official Day Z Twitter account has announced that the critically acclaimed ArmA II mod has surpassed 500,000 players.

For the uninitiated, Day Z is described as an open-world survival horror game, and if you own ArmA II: Operation Arrowhead, then you can download and enjoy it for free. It’s hailed by many as the best zombie game to date, and PC Gamer called it “one of the most important things to happen to PC gaming in 2012.” We agree.

Last weekend Day Z creator Dean Hall told Eurogamer that the mod was sitting on 420,000 users.

“Currently we’re running 22,000 concurrent at full peak, and 10,000 off peak, which is pretty huge numbers considering the original data structure and system was designed to handle 100 concurrents, and two servers,” said Hall at his recent Day Z Rezzed developer session.