As an ARMA II mod, DayZ has been around for years. But one year ago this week, Bohemia Interactive released the DayZ standalone. It's gone on to top the Steam sales chart, selling millions of copies.

　　But the game's success wasn't always guaranteed, key creative people explain in a new video released to celebrate the game's first birthday.

　　Check out the video above to hear directly from DayZ creator Dean "Rocket" Hall (who is leaving Bohemia at the end of the month to start a new company), as well as producer Brian Hicks and others.

　　Hicks explains that the true appeal of DayZ rests in its open-endedness.

　　"What makes DayZ really unique is it is effectively not as much a game world as it is a toolset for dynamic experiences," Hicks says. "People shape what the game is for them based upon their actions and how they play it. Every time you spawn in a new character, every time you join a fresh server, your experience will be different."

　　Though Hall is leaving Bohemia, that doesn't mean DayZ development is slowing down. Bohemia has named David Durcak the game's new project lead, and the developer has big plans for the game in 2015.

　　Bohemia published a new content roadmap for DayZ, following the one we saw last month. Notably, Bohemia is still aiming to have the DayZ console prototype ready in Q3 2015, while the game's full PC release remains scheduled for 2016. Below is the updated DayZ 2015 content roadmap.

　　First Quarter

　　Basic vehiclesAdvanced loot distributionNew rendererNew Infected AIBasic stealth system (infected and animals)DiseasesImproved cooking and horticultureAdvanced anti-hack system (Dynamic BattlEye)Second Quarter

　　Advanced vehicles (repair and modifications)Advanced animals (life cycle, group behaviour)Player statisticsNew UIPlayer staminaDynamic eventsWorld containersNew physics systemThird Quarter

　　TrapsBarricadingCharacter life span + soft skillsAnimal predators + birdsAerial transportConsole prototypeAdvanced communicationFourth Quarter

　　Animal companionsSteam community integrationConstruction (base building)Beta version