Were there any changes from Doom 1 to Doom 2 besides new additions?

I know that some of the textures from 1 aren't included in 2, but I was wondering if there were other changes.

Obviously map progression and intermission screens. The engine possibly had some bugs fixed and static limits increased at the time of Doom2's release.

15 hours ago, TurrboAnklet said:

I know that some of the textures from 1 aren't included in 2, but I was wondering if there were other changes.

1) A new weapon: Double Barreled Shotgun

2) New enemies: Pain Elemental, Chaingunner, Revenant, Hell Knight, Mancubus, Arachnotron, Archvile, Icon of Sin/Demon Spitter (Level 30 final boss), as well as the Nazis and Commander Keens in the Wolfenstein 3D-themed secret levels.

3) Megasphere powerup, which gives you 200% health and 200% armor.

^ I think those count as "new additions".

I think some things in the code did work differently compared to the Doom 1 of the time, with regard to a few line triggers and such, but then when Ultimate Doom was released those code changes got backported so vanilla Doom 1 as it's usually understood contains them now too.

Someone with more expertise on the inner workings of early Doom would have to weigh in to give you the details, but I know for certain that there are a few very early Doom 1 PWADs that do not work correctly on Doom v1.9 (probably v1.666 as well?) due to action trigger changes.

I believe that Lost Souls were originally part of the end-of-level kill tally as well, before Pain Elementals were a thing.

The maps were overall bigger and more complex

Getting rid of episodes and being one long progression was a huge yet small change

One change that irks me is that Lost soul's first two front-facing sprites were totally botched in a seemingly rushed and unfinished attempt to make it look "better" (and ended up doing the opposite IMO).