Garry’s Mod is one of the most popular things on Steam that isn’t a game. It’s a Mod for Half-Life 2 that came out exactly seventeen years ago and has allowed users to explore the physical model of Valve’s Source engine in ingenious new, mostly humorous ways. Mod got a standalone release two years later, but it essentially remained a tool and never grew into a game with which to have some pre-directed entertainment.
However, manipulating objects in a large sandbox is fun in itself, especially with Physics Gun, which allows users to freeze objects in space, and Tool Gun, which allows objects to merge and get interactive properties. An additional layer of entertainment is provided by user content that has been added through Steam Workshop support since 2012.
According to statistics from the end of 2021, Garry’s Mod has sold more than 20 million copies. A few years ago, a spiritual successor to the game called Sandbox was announced, which was developed in Unreal Engine 4. Development was paused in 2019 to switch to Source 2 engine in 2020 and has been in development ever since.
The Facepunch Studios development team in addition to this game later had even greater success with a hit known as Rust.