Garry's Mod

Garry's Mod (commonly abbreviated as GMod and typecased as garry's mod), is a sandbox physics game created by Garry Newman, and developed by his company, Facepunch Studios. Garry's Mod was originally a mod for Valve Corporation's Half-Life 2, but was later made into a standalone release in 2006 for Microsoft Windows, published by Valve Corporation. Later updates saw an OS X build added in 2010, and a Linux build in 2013.