Doom Classic Unity port

The Doom Classic Unity port is a series of official ports of Doom and Doom II initially developed by Nerve Software in cooperation with id Software and first published by Bethesda on as part of the "Year of Doom" promotional campaign. It was initially announced on stage during the QuakeCon 2019 (DoomCon) keynote presentation. The port is based on the Doom Classic codebase, but replaces the id Tech 4 shell with one based on the game engine. This offers immediate portability to a wide array of targets - the Doom and Doom II ports were available at launch for the Sony PlayStation 4, Nintendo Switch, Microsoft Xbox One, the app store for, and Apple's iOS app store.

Differences in Doom and Doom II
Note that many changes below are carried over from previous Doom Classic revisions.

Ultimate Doom and Doom II

 * Local multiplayer is available.
 * Cheat codes are available and accessible via the Options menu.
 * There is no confirmation when selecting Nightmare! skill.
 * On Nightmare!, the fast monsters mechanic has been removed entirely: fireballs shot by imps, cacodemons, barons of Hell and Hell knights are no longer sped up, and neither is the running speed of demons. Monsters retain increased reaction times.
 * The pickup sprites for the stimpack, medikit, and berserk (STIMA0, MEDIA0, PSTRA0) are modified in compliance with the Red Cross' wish that its symbol not be used in games. Instead, the symbol is replaced by a green cross.
 * The DMENUPIC that was the title screen in the original Xbox 360 version is used here.
 * Several monsters have the wrong death sounds.

Ultimate Doom specific

 * All animation from the intermission screens has been restored; they were originally missing from the BFG Edition.
 * The logo on E4M1: Hell Beneath has been removed, presumably to avoid trademark infringement.

Doom II specific

 * BFG Edition's MAP31: IDKFA and MAP32: Keen has been reverted back to MAP31: Wolfenstein and MAP32: Grosse alongside their respective map music, D_EVIL and D_ULTIMA.
 * The ZWOLF* texture with Nazi iconography (Hitler portraits, swastikas, Reichsadlers, etc.) have been censored. The definitions in TEXTURE1 are identical; it is the patches that have been changed.
 * MAP06: The Crusher has been edited to remove the linedef actions on the door track of the red key door which would crash the game.

Trivia

 * Doom and Doom II originally shipped with a much criticized Bethesda.net login screen upon startup (for the purposes of rewards via the Slayers Club), which was made less intrusive in a later update.
 * The music originally played recordings of a original songs at a noticeable reduced rate and wrong sound samples. This was later rectified with the update which uses recordings of the music played through a . Later still, the  update brought back direct MUS and MIDI playback.