Garry’s Mod started out as a simple modification for Valve Software’s Half-Life 2 that allowed players to goof around with the physics, models and other assets inside the game files.

Over the last six years, however, Garry’s Mod has taken on a life of its own, supporting every Source engine game under the sun, including Half-Life 2, its episodic expansions, Portal, Counter-Strike: Source, Left 4 Dead and Left 4 Dead 2, as well as blossoming into a full retail title.

Now it’s on the Mac, having been released by Valve through their popular Steam for Mac digital delivery service. Steam is having a 50% off sale on the title right now, so it costs only $4.99… although you should be aware that to actually use Garry’s Mod to make elaborate Rube Goldberg machines or — as in the videos embedded above and below — absolutely hysterical internet videos, you’ll need to own at least one Source engine game.

Check out some of the more classic products of Garry’s Mod after the jump.

httpvhd://www.youtube.com/watch?v=OHxyZaZlaOs

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