Anyways, besides Extreme Bunker I've done most of the Arty's Memoir stuff so I'll review all the modes while they're still fresh in my head
Bunker
The main mode of the game. It's a pretty decent stealth challenge, with most of the game being getting keys in good spots and the rest hoping that Boofie doesn't kiss you as you bring them to the entrance. Having your movement slowed while holding keys creates a lot of tension, although nerfing your Stamina until crouching until fully rested seems sort of unfair. Having to track down the key again seems fair punishment enough. Also side note, but I feel like the Stamina/Power limits could've been implemented into some of the other modes. The lamp is also pretty useless in other modes so I wish more was done with that.
Another criticism I have is with Boofie, you either hear him or you don't. The volume of his squeaks doesn't vary much and he's also very hard to hear when he's above/below you (traversing between the basement and main floor via stairs has gotten me killed so many times), leading to determining his location being somewhat of a guessing game. This builds tension, but not in a way that feels consistent.
The atmosphere of the mode is pretty nice though. The bunker becoming darker is a great mechanic and the unique ambience of the keys really adds to the "dreamlike" nature of the game. The bunker itself is also very uncanny, a trait shared by every map in the game, due to the subtle differences in consistency such as Boofie and the keys having an ungodly amount of polygons compared to everything else. The pixelation filter covers things up well though, and while some may call it lazy I personally think it's an appropriate stylistic choice that fits well within the game.
Maze
Can be annoying due to the issue with determining Boofie's location discussed earlier, but I've found that with patience the mode is more than doable thanks to Boofie leaving himself open by "patrolling" the various open areas in the map. Hiding is sometimes difficult however, and navigating the maze itself can be disorienting at times due to its narrow corridors in comparison to the player's speed. Seriously, this is the only mode with no Stamina limit in which I don't run, but I guess it adds another element of skill in evading the Boofies.
Arcade
Probably my favorite mode in the game, it also fits very well with the game's atmosphere. However, it's still a bit prone to RNG, for example say the alarm and phone go off at the same time, the green guy is patrolling below, and the blue gal is in both of the rooms you need to be in. I'm not exactly sure how lenient these characters are with situations like these but on harder difficulties I was definitely pushed into some stressful scenarios. And while the other characters all add enjoyable elements into the level, I wish more could've been done with the orange dude. The orange dots are way too easy to avoid, especially since you're either running away from something or camping in one room in that mode.
Kitchen
In my opinion, the most RNG dependent mode on harder difficulties, although it also has an amazingly unsettling atmosphere. I absolutely adore the background audio, and the liminal nature of the environment (ie the corridor Boofie arrives from) was done great here.
Gamla (the only name I remember due to dying to her so much!) is often nearly impossible to evade on higher difficulties if she decides to just go to your floor if you're in an odd spot. There also aren't really that many good places to hide from her, despite that being the main gimmick of the level. Although hiding from Boofie in conjunction with keeping track of Gamla provides great tension. The small black burgers are also an interesting element and pretty fair since they can't chase you and don't go to hiding spots.
I also wish more was done with the idea of having a map based on verticality. If there were more floors and Gamla worked a bit different it would probably be one of the best modes in the game but as it stands it's just good.
This mode also has one of the more interesting secrets. It's probably only possible on Easy mode due to the lack of a time limit but it was a nice challenge akin to getting the keys one-by-one in the bunker. It probably goes on for a bit too long but having to survive in the kitchen for an uncomfortable amount of time is probably the point.
Backrooms
My personal favorite mode. The Kinetic and Static Images have great designs and the level itself has some of that juicy lore with the notes. Extreme mode in particular is very enjoyable due to the pressure of getting all the notes before the Kinetic Image enrages. Planning a route through the map is a very interesting experience, with you having to adapt to the differing note locations every time (spotting them on the landmarks can also be tricky at times, adding to the tension). However I wish there were less dead ends, but that's probably a skill issue on my part.
Christmas Challenge
The map and atmosphere is great here, very uncanny especially with that one cabin with the Boofie balloons and the appearance of Blitz himself. Like WHAT even is he?! Part of the difficulty of the mode is knowing where all 30 presents actually are, but once you get a route down it's pretty straightforward, sometimes to a fault so maybe a bit of randomness would've been nice. Stealing Boofie's hats is also fun.
Valentines' Challenge
It's basically Pac-Man. If it didn't have a map I would've probably hated it but because it does it creates a very unique, stressful, but overall fair challenge. The design of this level is also incredibly weird, I love all the random stuff attached to the walls, and the Oui-Ouis and their doors have great designs. My only complaint is the lack of an endless mode because there's definitely potential for that.
Yeah lots of text here but that's what you get for making all the modes so different :P although I enjoy the craziness. I also understand that it's your first game so don't take my criticism too hardly, I just like getting my thoughts out more than anything. I'm super excited to try out Elaine's Memoir but for now I just gotta suffer through Extreme Bunker. Eventually...
Also love your YT content especially the AEwVS vids and you forcing Mystman12 to play ABiBaZ. Although with the controversy surrounding MrDrNose I understand if you don't wish to continue that series.
Best of luck in the future, whether it be on Steam (we can hope) or on YouTube!