Like its predecessors, Quake and Quake II, Quake III Arena can be heavily modified, allowing the engine to be used for many different games. Mods range from small gameplay adjustments like Rocket Arena 3 and Orange Smoothie Productions to total conversions such as Smokin' Guns, DeFRaG, and Loki's Revenge. The source code's release has allowed total conversion mods such as Tremulous, World of Padman, OpenArena, and Urban Terror to evolve into free standalone games.