The creator of the incredibly popular Garry's Mod has revealed that more than 7 years after the release of his game on Steam, sales still continue to rise.

Since release, the game has managed to sell more than 3.5 million copies, with the charts peaking in July of this year, most likely due to the Steam Sale going on at the time

Speaking to RPS, Garry attributed the continued success of his game primarily to user created content. Of particular note are the Youtubers who continue to popularise his game.User generated content plays a massive role. Other factors include:

Steam’s ever increasing popularity.

Some of the gamemodes in GMod are like games of their own – so when a new gamemode gets released more people buy.

Team Fortress 2, Portal content. People play the games and want to play with their contents… we made sure to allow that stuff as much as we could.

Team Fortress 2 going free to play must have attracted a lot of people to the universe.

When Source Filmmaker was released a lot of people said things like “Valve just KILLED GMod”. But I’m guessing a lot of people unaware of GMod played with SFM, made a movie – and wanted a stupid effect that they’d seen in another movie… which was made in GMod. So they got it.

Minecraft. You’d think Minecraft would kill GMod’s popularity… but it’s kind of the opposite. People play Minecraft to death – they love it.. so they go out looking for other games that are a bit like it. Minecraft has attracted a lot of people that aren’t really PC gamers too. They play the game on the 360 or the iPad and everyone tells them that the PC version is better.

And of course Steam Sales.