Garry’s Mod is a sandbox mod for the Source Engine. Unlike normal games there aren't any predefined aims or goals. Players are given tools and are left to entertain themselves. The player is in a world where objects can be created and destroyed on demand. Where people can be created and destroyed with the click of a mouse. A world made for him. A world he made.
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This is Dr HAX from toybox but its packed up as an addon for multiplayer.
I take 1% credit for packing this as an addon.
The rest is to its respectful author.