17-year-old Gus Dubetz, or Gusmanak, started using ROBLOX in 2008, due primarily to a life-long fascination with physics. By 2010, Dubetz decided to take a short break to focus on clay and wood sculpting.

It wasn’t until two years later, shortly after the release of Day Z, a hugely popular add-on to ArmA 2, that Dubetz, with long-time friend and scripter Ethan Witt (aka ZolarKeth) asked, “what if we went back?”

That question lead to the birth of an idea—Dubetz and Witt didn’t just want to make another “generic shooter”, they wanted to make a full blown game—something with ambition, scope, replayability, and, most importantly, zombies. That idea became Apocalypse Rising.

“What makes our game unique is that it’s different every time you play it. There are different perks, people to play with, places to explore—half the game is randomized,” says Dubetz.

Dubetz was able to do this by organizing items into different types of “spawners”—general loot, general weapons, military general, military weapons, and medical were categories taken into consideration.

“Each spawner is a brick,” explains Dubetz. “With this system, it’s possible for one ‘loot brick’ to spawn nothing at all, or even two of the same item. General item spawners can spawn zero to four items,  whereas weapon spawners can spawn nothing, or a weapon with one to three magazines.”

Outside of the random nature of the worlds, the gaming system itself is quite deep. You can choose from one of four classes, each accentuating one skill (i.e. the Ninja perk makes you quieter, the adrenaline perk refills your health, etc.), and find a myriad of weapons throughout the world, from pistols and pipes, to shotguns and rifles.

Much like Day Z, rationing supplies is a big part of staying alive. Bullets are scarce, so lining up headshots is extremely important, especially after surviving a few “days,” when zombies begin attacking more frequently and in larger groups. You also have the option of joining up with fellow players to face the undead as a team, but keep in mind, not all players will see you as an ally and may even kill you to take your items.

ROBLOX Creative Director John Shedletsky got to spend some time playing Apocalypse Rising, and found the group aspect to be one of the most interesting parts of the game.

“You never know when one player will decide he is desperate enough for supplies and will try attacking and robbing you of all your loot,” says Shedletsky. “It creates a really interesting tension. I killed a man for a can of beans.”

To address this danger, Dubetz came up with the “Bandit System”, which essentially marks people with bandanas who have killed three or more survivors intentionally. There is an important distinction between bandits and those forced to kill in defense, so the basic rule is this: if you come under fire and kill your attacker, you won’t become a bandit.

Dubetz and Witt spent months planning, then finely crafting, every aspect of the game. The idea was simple: to recreate Day Z, their favorite PC game, in the world of ROBLOX.

“We were inspired most by the idea that we could take a really great game, and challenge ourselves to recreate it in ROBLOX,” recalls Dubetz. “This was something nobody had ever done before. This was our new challenge”.

Dubetz was concerned that the ROBLOX engine wouldn’t be able to handle a game of such scope, and figured that if the ROBLOX engine wouldn’t be able to handle his vision, then that vision wasn’t worth pursuing.

“The more things we added, the more lag we started to notice,” says Dubetz. “Over time, we just had to figure out our limits, and just how far we could go within the engine.”

Eventually, Dubetz and Witt settled on a look and aesthetic they were happy with, and it’s a good look indeed. What strikes you immediately upon starting up Apocalypse Rising is the eerie atmosphere. When day turns to night, an unsettling fog blankets the bleak environment, obscuring your vision. You’ll want to see as far ahead as you can, so playing in first-person mode is the way to go. The massive level makes you feel like one of the few remaining humans on earth, and finding scattered journals adds small, creepy bits to the story.

Less than 15 hours after releasing the title, Apocalypse Rising had hit the front page. At the time of this writing, Apocalypse Rising has been played 953,869 times.