Classic Doom various guides

https://www.doomworld.com/vb/doom-editing-tutorials/74073-vanilla-level-editing-lesson-1-preliminary-reconnaissance/
https://www.doomworld.com/tutorials/
https://zdoom.org/wiki/tutorials
http://doomnexus.drdteam.org/tutorial.html
https://zdoom.org/wiki/Richard_Clark%27s_tutorials
http://www.realm667.com/index.php/en/tutorials-mainmenu-138
https://doomwiki.org/wiki/Editing_tutorials
https://doomhell.com/index.php/2019/07/28/doombuilder-guide-1-setting-up-doombuilder/
https://doomwiki.org/wiki/Tips_for_creating_good_WADs
https://www.doomworld.com/forum/topic/107024-new-to-mapping
www.doomworld.com/forum/topic/107334-keeping-levels-visually-interesting-outdoors
https://www.youtube.com/watch?v=REiGGiygbbE