Alright, so a few thoughts!
* Speed: Many vanilla Doom maps and custom maps with strict compatibility rely on speed for platforming challenges. The player moves so unreasonably slow that many of these challenges are impossible to complete. As an example, Map06 in Doom 2, in order to get the blue keycard you have to ride a lift to the top and then run over a gap onto a platform to press a switch and lower another lift. The player is far too slow to make this jump, and even then, still too slow to make it to the second lift containing the blue card in time. I'd either bump the movement speed up a few notches, or have the sprint function boost the player's speed up significantly at the cost of, say, having to lower your weapons or something, kinda like how Hideous Destructor handles it.
* Weapons: Overall the weapons feel like they could do with a bit more OOMPH, if you catch my drift. Many of the weapons' firing sounds feel weak and unsatisfying. I'd also perhaps boost the damages for some weapons as well, such as the 9mm weapons since it feels like you just chew through ammo with them. It also wouldn't hurt to find more interesting sprites for them as well. I know full well how difficult it can be to find good sprites that are available for public use, and lack the skills myself to make good sprites, but there are other weapon sprites available out there! A specific gripe goes towards the .45 revolver. I do like how it realistically has a heavy trigger pull like a double action revolver would IRL, but I'd recommend being able to cock the hammer back with the alt fire so you can prep a shot and not have to deal with the lengthy trigger pull, since that ABSOLUTELY can mess with your shots.
Also two random gripes: The sprite for the 9mm ammo box looks like it says 9x18, not 9x19
Had me a bit confused and wondering if I'd find a Makarov somewhere lol. I also wonder if the fists are supposed to be as strong as they are, cause I can bag pinky demons with just three punches, and that feels unreasonably strong to me o.o
* Weapon Slots: Man, I do miss being able to press a hotkey and swap to another weapon. It is obnoxious that you can only carry one weapon in your hands and have to sort through your inventory to pull your other guns out when needed. I'm not against limiting how many weapons you can carry at any given moment, though! In my opinion, having a default of a handgun slot, a melee slot, and a long arm slot (as well as the ability to pull your fists out without having to drop your gun) would lead to making the gameplay much less frustrating while still keeping it interesting with limiting what you can carry at any given moment. Could also add special backpack items that allow you to carry more weapons on your person as well, like an extra holster or sling strap!
* Inventory: This is the thing I probably have the most gripes with. I genuinely LOVE what you've done here! A slot based inventory system must have been an absolute nightmare to code up in the Doom engine, and it functions pretty well once you get used to how to work it! Took me a bit of time to learn that you can press Use to exit menus, and once I'd learned that it felt much less clunky. Good on ya for that, dude! It's a fantastic system that I feel has an absolute butt ton of potential for fun and unique gameplay additions. THAT SAID THOUGH, you're not given enough inventory slots at all. Five inventory slots to begin with is cruel and limiting to the point of reducing the fun you can have. There's an art to balancing the player's needs and limitations in a survival horror game/mod, but when everything you need and use takes up the same amount of inventory space and your carrying capacity is limited that severely? It becomes needlessly frustrating. Guns, meds, ammo, repair kits, all take up their own spaces in your inventory. This I am not against as a concept, just so long as you can actually carry enough. The extra backpacks that you find to increase your carrying capacity therefore feel less like a reward to the player, but instead like an absolute necessity, and even then it still feels like it isn't enough! I've still got plenty of maps to get through in Doom 2, but I don't see myself ever hitting my weight cap because of how little I can carry in my inventory in the first place, and I am fearing the more difficult crowds later on in the game since I likely won't have the hardware to handle big crowds of high health monsters when I'm limited to carrying VERY little in terms of weaponry and ammo.
* Monsters: Not much to write home about here since it's just the vanilla monsters with extra zombies, but those extra zombies need more visual flair. At a glance it's impossible to tell the difference between a zombie with a Beretta, a zombie with a Glock, a zombie with a Revolver, a zombie with a Colt handgun, or a zombie with a micro uzi. They all look the exact same, and while they have different firing sounds, these sounds (with the exception of the glock) are all different from the sounds the players' weapons use, which can add a bit of confusion.
It also feels weird to say this, but I am missing the presence of pump action shotgun zombies and zombies wielding automatic long arms. There's a lot of weapons you can use in this mod, but it'd be nice if the zombies you face used more of those weapons as well, as a way to help get them into the player's hands and to help give you their ammo as well. Editing this because yes, tougher zombies with tougher guns to start appearing the farther into a map set you go. Adaptive difficulty, I seriously love it! I should do something similar for my own survival horror mod.
* Armor: An interesting system for certain! Being able to uniquely equip body armor, headwear, and boots which all boost your armor rating is definitely a neat thing, and I feel it has a LOT of potential. Special boots to help you wade through damaging floors, helmets with built in targeting systems to increase your accuracy, body armor with pouches to boost your carrying capacity, tons of different things you can do with it! I look forward to seeing what you do with this.
* Item Condition: A lot of people out there complain about how stupid item degradation is in games, and I mostly disagree with them? If your gear degrades too quickly it can be frustrating, but here it's fine! Weapons and armor hold their condition pretty well and don't need to be repaired too frequently, and repair kits are in ready supply, so it's never a detriment in my opinion. I know that armor with lower condition will protect you less and less, but how does it affect weapons and backpacks?
* RPG System: I ain't got too much to say here, since its presence is kind of a light one it feels. I'm just a little bit unsure as to what the heck the Charisma stat does, as well as what leveling up your weapons stats does for you. I can understand being able to heal more with a higher healing skill, but does a high small guns skill affect accuracy? Damage? What does it do? And the pickpocket skill, is that supposed to be the stealth skill to boost how good at sneaking and back stabbing you are?
* Corpse looting: A nifty concept and one that works pretty well for the most part! Two things I wanna bring up though. For one, it'd be nice if I could use items out of a zombie's inventory. Find a stimpack and wanna immediately use it, ya gotta put it in your inventory first and then either press the hotkey button for it or close out of the loot menu and into your own inventory to use it. Two, it'd be nice to have the ability to move and drag corpses around. Often times corpses will be sat on top of one another and this makes it incredibly difficult to try to loot every one of them.
Overall, nice work man. This feels like a proof of concept, and that concept has been proven. I'm gonna be closely following this mod to see how it develops over time, and am excited to see how you improve it over time! Keep up the good work!
