Over the weekend Facepunch Studios founder Garry Newman announced that Garry's Mod, the physics engine playground that got its start as a Half-Life 2 mod, has now sold over 10 million copies.
That's notable because Garry's Mod has been sold on Steam since 2006, yet only hit its 1 million sales milestone in 2011. Thus, in the five years since it sold a million copies it's sold 9 million more, a remarkable sales jump.
Sales of Garry's Mod have been gaining steam for years, and in 2013 Newman hypothesized to Rock Paper Shotgun that the game was growing ever more popular thanks to the advent of YouTubers and the rising popularity of creative sandbox games like Minecraft.
Newman noted last year in an interview with PCGamesN that Facepunch is "kind of working on a sequel" to Garry's Mod that will be VR-focused while also continuing to develop Rust, its remarkably popular online survival game that launched on Steam's Early Access service in 2013 and has since sold over 3 million copies.