Two years ago, the “DayZ” mod was developed for Bohemia Interactive’s military simulation game, “Arma 2: Combined Ops,” introducing fans of the zombie horror survival game genre to a more realistic take on a post-apocalyptic scenario.

The original “DayZ,” mod which was developed by Dean “Rocket” Hall launched on April 28, 2012, featuring highly realistic elements absent from past zombie survival games. Players first introduced to “DayZ” in April 2012 quickly discovered these many realistic elements as they explored the fictional post-Soviet state of Chenarus, including bone fractures, infections, fainting from low blood pressure, thirst, hunger and other body conditions.

By implementing the many realism features of “DayZ,” Hall forced players to adapt play styles from one focused on first-person-shooter style play, to gameplay focused on survival. Players of the “DayZ” mod started out with nearly nothing, forcing players to scavenge cities and towns for basic needs, while also gathering weapons to defend with, all while avoiding zombies and other human players who may or may not be looking to steal loot from players.

Over the course of its life as a mod, “DayZ” has been praised for its unique gameplay.

Three months after its 2012 release, over one million unique users were registered playing the “DayZ” mod. The mod was so successful upon its release that it has also been credited with triggering the surge of 300,000 purchases of the 2009 military simulator, “Arma 2” sending the aging military sim to the top of the sales charts on the Steam game distribution platform.

Eight months after the “DayZ” mod was first released, it was awarded “Mod of the Year 2012” by PC Gamer, who praised the game for its “hands-off” approach to its gameplay.

Following the success of the “DayZ” mod, Hall was eventually brought on by Bohemia Interactive as project lead to develop a standalone version of “DayZ,” which launched in an alpha state as part of Steam’s Early Access program on December 16, 2013, after missing its original target launch date of December 2012.

Despite the delays prior to the release of “DayZ” standalone and its unfinished state, the zombie horror survival game developed by Hall and Bohemia Interactive has continued to see success with nearly two million copies sold through Steam.

What’s next for DayZ isn’t exactly clear, as Dean “Rocket” Hall is expected to leave Bohemia Interactive by the end of 2014. However, development of “DayZ” is expected to continue even after Hall’s departure, as Bohemia Interactive continues to add features, optimize graphics and server code.