Doom 3 (Remake)/References

Doom and Doom II

 * The entirety of the original Doom and Doom II: Hell on Earth unlockable as a side-game via inputting the passwords "ULTRAVIOLENCE" and "MISSUDAISY" as the opening password to the computer in Sergeant Kelly's bunker. The game itself is modified significantly from the original.
 * There are twelve new weapons, bringing the number of weapons available to the player up to just over double the original amount. In addition to this, the Super Shotgun from the second game is now available in the first game. There is a option to exclusively use the original loadout alongside two of the newly introduced weapons, known as "Boomer".
 * The Axe, based upon the weapon from Doom RPG and used as both an alternate melee weapon that can kill the lightest enemies in a single hit or break down certain doors. It is equipped under weapon slot 1 with the Fists.
 * The Auto Pistol, functioning like a faster version of the HacX pistol and resembling the unused gun seen on the original cover art. It is equipped under weapon slot 2 with the Pistol.
 * The Machine Gun, based on the scrapped concept from the original game and functioning similar to the machine gun in the main game. It is equipped under weapon slot 4 with the Chaingun.
 * The Unmaker, a scrapped weapon from the game's planning stages that was later included in Doom 64 that functions akin to a railgun and does not possess ammo pickups, instead gaining shots by killing enemies. It is equipped under weapon slot 7 with the BFG 9000.
 * The Grenades, which function similar to the grenades in the main game. They are equipped under weapon slot 8.
 * The Fire Extinguisher, based on the Doom RPG weapon that is used to extinguish fires to allow access to certain secret areas as well as damage certain enemies such as the Pain Elemental. It is equipped under weapon slot 8 with the Grenades.
 * The Dark Claw, another scrapped concept from the beta of the original that functions as a continuous beam of mid-range highly damaging energy with no individual ammunition, instead slowly draining the player's own health to power it. It is equipped under weapon slot 9 with the Chainsaw.
 * The original weapons are changed somewhat to accommodate the new playstyle.
 * The Chainsaw is equipped under weapon slot 9 rather than weapon slot 1.
 * The difficulty levels are changed, and some new skill levels are added. All difficulties also have their own humorous descriptions when clicked on.
 * "I Wanna Play, Daddy!": "For younger players, gamers unfamiliar with first-person shooters, and video game journalists." The player takes 25% of the base damage, starts equipped with the Fists, Axe, Pistol, Auto Pistol, Shotgun and Machine Gun, and begins each level with full health and Blue armour. Enemies take 200% of the base damage and come in half their base numbers.
 * "I'm Too Young To Die!": "You're not invested in the challenge. You just want to kill demons, and that's not a crime." The player takes 50% of the base damage, starts equipped with the Fists, Pistol, Shotgun and Machine Gun, and begins each level with full health and Green armour. Enemies take 150% of the base damage and come in three-quarters of their base numbers.
 * "Hey, Not Too Rough!": "Easy does it! You want to blast demons without having to worry TOO much." The player takes 75% of the base damage, starts equipped with the Fists and Pistol, begins each level with full health, and armour carries over between levels. Enemies take 125% of the base damage and come in their base numbers.
 * "Bring It On!": "The standard Doom experience. Hold off the demon invasion and have fun doing so!" The player takes 100% of the base damage, starts equipped with the Fists and Pistol, and health and armour carries over between levels. Enemies take 100% of the base damage and come in their base numbers.
 * "Hurt Me Plenty!": "If you're not a Doom expert, you will be by the time you complete this difficulty." The player takes 125% of the base damage, starts equipped with the Fists and Pistol, and health and armour carries over between levels. Enemies take 80% of the base damage and come in their base numbers.
 * "I Own Doom!": "You talk the talk, but can you walk the walk? Anyone who completes this difficulty gets our respect." The player takes 150% of the base damage, starts equipped with only the Fists, and health and armour carries over between levels. Enemies take 60% of the base damage and come in double their base numbers.
 * "Watch Me Die!": "An absolutely unfair difficulty reserved for the baddest of the bad. Good luck ... you're gonna need it." The player takes 200% of the base damage, starts equipped with only the Fists, and begins each level with 50% health and armour. Any health gained above 100% will gradually drain until it returns to 100%. Enemies take 40% of the base damage and come in triple their base numbers.
 * If played on the two hardest difficulties or with the "Survival Horror" setting turned on, the game will be darker and use the PlayStation Final Doom soundtrack.
 * The standard green Armour absorbs 50% of all incoming damage rather than 33%, and the blue Megaarmour absorbs 75% of all incoming damage rather than 50%. Having any armour also reduces the amount of incoming damage the player takes by 20% with the green Armour and 40% with the blue Megaarmour.
 * The Backpack is redesigned to resemble the backpack in the main game, which is in turn a updated retooling of the original design.
 * The Super Turbo Turkey Puncher 3 game, which uses the fist sprites from the game, is retained.
 * The famous IDDQD (god-mode) and IDKFA (all-weapons) cheat codes can be entered in-game. Doing so will instantly kill the player with the message on-screen of "Trying to cheat, eh? Well, now you die!", award the player the "Nice Try!" hidden achievement and send them back to their last checkpoint save.
 * Secret Level 33, the final secret level of the game, is a recreation of the legendary first level of the first game, Hangar, also known as E1M1.
 * The "Nightmare" difficulty was originally the hardest difficulty of the games, but is instead the second-easiest difficulty of the main game.

Doom 64

 * The main uniform armour worn by the Marines resembles the armour worn by the protagonist of 64 with some elements from the armour worn in the original Doom 3.

DOOM Eternal

 * Eternal noticeably ties into the game's storyline, with
 * A advertisement for the game pokes fun at Eternal with its tagline "No magic swords. No useless arm blades. No ugly, overcomplicated, edgy Tolkien wannabe stories. No backstabbing AIs, and no puke-green heavy metal Warhammer 40k rejects. Welcome to the real word, bitch." The humour of this is ironic, as all these events appear in-game.

References to Other Doom Fanworks

 * The famous Hissy plush Cacodemon, made by Jonas Feragen, appears in Sergeant Kelly's personal quarters on his bed.
 * The infamous "so bad it's good" fanfiction Doom: Repercussions of Evil is referenced by the Imps writing on the walls in blood "JOHN IS A ZOMBIE", "YOU WILL BE KILL BY DEMONS" and "YOU ARE THE DEMONS".

References to Other Games

 * The secret levels of the game, with the exception of the first, second, fifth, tenth, twenty-fifth, thirty-first, thirty-second and thirty-third, are all recreations of levels in past first-person shooter games.
 * Secret Level 9 is a heavily modified recreation of the Team Fortress Classic version of the Team Fortress series' iconic map, 2Fort. Its placement is also a reference to the main number of classes in the games.
 * Secret Level 14 is a recreation of the seventh level of the fourth episode of Quake, Azure Agony. Its placement is also a reference to the original size of the file, 1.4 MB.
 * Secret Level 30 is a recreation of Spaceport from Duke Nukem 3D 's second episode. Its placement also references the game's subtitle, with the number 30 standing in for the word 3D.
 * The famous Dopefish from id Software's Commander Keen series appears on the front cover of a book on the desk in Sergeant Kelly's personal quarters.