id Software has developed their own game engine for each of their titles when moving to the next technological milestone, including "Commander Keen", "Wolfenstein 3D", "ShadowCaster", "Doom", "Quake", "Quake II", and "Quake III", as well as the technology used in making "Doom 3". After being used first for id Software's in-house game, the engines are licensed out to other developers. According to "Eurogamer.net", "id Software has been synonymous with PC game engines since the concept of a detached game engine was first popularized". During the mid to late 1990s, "the launch of each successive round of technology it's been expected to occupy a headlining position", with the "Quake III" engine being most widely adopted of their engines. However id Tech 4 had far fewer licensees than the Unreal Engine from Epic Games, due to the long development time that went into "Doom 3" which id Software had to release before licensing out that engine to others.