There's probably some errors and missing stuff but i thought it should be big enough for someone to get clear information.
Some stuff could be suggested (What else to explore about the series and its history, some technical stuff, gameplay pro tips, stuff about settings, intructions, certain ports/source ports/versions being mentioned, differences between those etc) so if possible, leave that in the comments.

It starts here/below:

  • Here's some instructions manuals from the originals if you're interested in even the otherwise, not important story.

https://www.retrogames.cz/manualy/N64/Doom_64_-_Nintendo_64_-_Manual.pdf

http://www.wolfensteingoodies.com/archives/olddoom/home.htm (CTRL + F and search for "Original Doom Manuals")

Also, if you want to get into the games, here's some info:

  • The classic Collection/Bundle on Steam or GOG has Ultimate Doom (First game with an additional fourth episode), Doom 2 (Which has the Master Levels) and Final Doom (Two 32 maps episodes, which are a bit more difficult and not as enjoyed as the main two games) (I also think it's the GOG version that has a fix for a problem with TNT's map 31).
  • (As of editing this, in August 2022 id changed some of their games' listings, so this classic bundle mixes up the original version of 1/2/3 with their Unity/BFG versions and even include Doom 64 in, so expect some info here to be outdated).
  • Most people play Doom with source ports and there's a lot of them for Doom games.
  • Chocolate Doom is the most faithfull one, while Crispy Doom is like a slighty "friendlier" version of Choco offering some options.
  • PrBoom and PrBoom+ work as vanilla source ports with some additions. I think the latter can play maps that are still vanilla but have lots of enemies if i'm right (There's also better demo support i believe).
  • Forks like DSDA-Doom https://www.doomworld.com/forum/topic/118074-dsda-doom-source-port-v0150/ and MBF https://doomwiki.org/wiki/MBF are based on the Boom lineage of ports and have their own features and changes too.
  • GZDoom is for gameplay mods, advanced modding projects and has a lot of settings and features. It's more advanced than other source ports but it's not as faithfull (Either due to some default settings or outright changes), some of its default settings are kinda bad (You can change them if you can browse the options menus) and can be a bit heavy on certain hardware (Which means PrBoom+ can handle huge maps better, if i got that right).
  • Some mods may require later/previous/specific versions of GZDoom or even the now abandoned ZDoom.
  • The Eternity Engine https://doomwiki.org/wiki/Eternity_Engine has some features similar to the ZDoom family and while not as popular, it is home to some very good maps.
  • Zandronum is also mod focused but for multiplayer.
  • Odamex is another MP source port and this one seems to be vanilla focused.
  • ZDL is a launcher that allows you to set up orders for which content you want to play (Such as a mapset, then one or two gameplay mods after it). Normally, you put the maps/wads before the gameplay changing stuff, while selecting a specific IWAD, that the map/mapset/wad is made for (Other launchers exist too and some could be better).
  • IWADS (As in, the games themselves like Doom 1, 2 etc) should be in the same folder as your chosen source port but source ports themselves should be on seperate folders. (Which means you may have to copy+paste the IWADS into each seperate folder) (There may be a better alternative to this)
  • To find the IWAD files, this should help https://i.imgur.com/7fe8XmB.png
  • To get mods or wads, you can check sites like Doomworld's idgames, ZDoom forums, ModDb or maybe simply google mod related stuff and see if a forum thread or video description have a download link. Doom modding/mapping is big enough that there's a lot of places to get that content. Even Realm667 posts about latest mod/map releases at times.
  • There's also YT channels dedicated to Doom mod stuff and even Tumblr/Wordpress blogs and Twitter accounts.
  • Doom 64 had its own source port (Which was Doom 64 EX, but it required a Nintendo 64 ROM of the game) and there's the official port from the same guy behind Doom 64 EX which seems to be more advanced and include new levels.
  • There was a PS1 Doom port that was amazing despite its differences from the pc version and it has a TC (From fenderc01 i think) that you can play on pc.
  • SIGIL is a 5th episode from John Romero himself and it's set after Thy Flesh Consumed, so it's also hard like that episode. It's also free but you can also order some tracks from Buckethead and a box or something.
  • If you want to play Doom 3 (And its expansion Resurrection of Evil), you could see the original game and its expansion and mix them with the duct tape mod, if you're worried about the changes in the BFG edition.

https://doomwiki.org/wiki/Doom_3:_BFG_Edition#Differences_with_Doom_3

https://www.doomworld.com/forum/topic/113479-list-of-things-removed-in-doom-3-2019/

  • Doom 2016 is great for a modern shooter and if your PC is good enough it'll perform great and while most of the praise centers around the single player, you may have different opinions on the multiplayer and SnapMap.
  • Its sequel, Doom Eternal, builds up on the formula and could be harder, but more exciting, while its multiplayer BattleMode could be a bit more niche in comparison to the singleplayer.
  • Opinions over The Ancient Gods expansions can very, based on gameplay or story, but there are things there to like.
  • Speaking of info, the wiki i linked to you above is what most fans use instead of the Fandom version.
  • Doom also had mobile spin-offs such as the RPG series and Resurrection but most of these are hard to find, have little documentation and require emulation, even if there's reverse engineering projects for them.
  • Though D1RPG has a fanmade PC port that is really good https://www.doomworld.com/forum/topic/129997-doom-rpg-port-reverse-engineering/

I tried to add as much info as possible and someone once made a Doom guide, so i hope this one guide i found can work too.

http://thathomestar.tumblr.com/post/107549841357/how-to-doom-part-1-getting-set-up

Also, here's this for some gameplay tips.

https://www.youtube.com/watch?v=HJcf0aOwmiA

https://www.youtube.com/watch?v=_0KBAZkPFmI

And someone on YT called Decino made videos about Doom's gameplay and it should help you.

https://old.reddit.com/r/Doom/comments/cezqa4/mods_to_play_before_doom_eternal/ and

https://old.reddit.com/r/Doom/comments/b94wek/kinda_mega_thread_about_doom_modwad_recomendations/

Ends here.

If there's something else worth adding, then suggest some ideas.

Edit
Pub: 31 Aug 2022 13:12 UTC
Views: 126