Doom engine

The Doom engine, also known as id Tech 1, is the game engine that powers the id Software games Doom and Doom II: Hell on Earth. It is also used in Heretic, Hexen: Beyond Heretic, Strife: Quest for the Sigil, Hacx: Twitch 'n Kill, Freedoom, and other games produced by licensees. It was created by John Carmack, with auxiliary functions written by Mike Abrash, John Romero, Dave Taylor, and Paul Radek. Originally developed on NeXT computers, it was ported to DOS for Doom's initial release and was later ported to several game consoles and operating systems.

The source code to the Linux version of Doom was released to the public under a license that granted rights to non-commercial use on December 23, 1997. The source code was later re-released under the GNU General Public License on October 3, 1999. The dozens of unofficial Doom source ports that have been created since then allow Doom to run on previously unsupported operating systems and sometimes radically expanding the engine's functionality with new features.