Creaky Corpse's MMO Dead Frontier now has over ten million registered players and 100,000 players per day.
"I'm hugely grateful to everyone who's played Dead Frontier and helped us to reach this epic milestone," said the game's creator Neil Yates.
"I find it hard to comprehend that something I made mostly while sitting in my bedroom has become so popular. I mean, ten million is such a crazy number. That's a moderately sized country right there."
The free-to-play zombie MMO was released in 2008 and Creaky Corpse is currently concentrating on another MMO, the gladiator themed Doom Warrior.
I think the biggest limitation is definitely time, Yates told the Unity blog last year, explaining that he did all the programming and design.
Single-player games are hard enough work, but an MMORPG is just insane! Just keeping one up and running takes a lot of effort. Then you have to fix bugs, add new features, new content, run events and competitions. It's taken me 5 years to get Dead Frontier to its current state, and I still have loads of things that I need to add.