Garry’s Mod is a modification based on the Half Life 2 engine. It represents a physical “sandbox”, which allows the player to manipulate objects and to experiment with physics and realism supported in the Source engine. This modification was created to demonstrate the vast possibilities of the Source engine, which are limited only by the players imagination. For a proper functionality of Garry’s Mod, you are required to have a game based on Source engine (example: Half-Life 2, Counter-Strike: Source, Team Fortress 2 or Portal) and of course a computer that satisfies at least the minimum requirements.
Still great in 2018. Just checked!
Play this creative mode for Source engine now, just click on the link below to receive a full no-steam version of Garry’s Mod.