I love you.
So much good stuff, I agree with a lot of things and some of the stuff made me rethink things. I'm going to try to touch on most things but even if i dont i'll take this with me. What makes me happy is that you're probably the first to figure out some of my design decisions, which shows that you actually played it.
Movement: I'm not using Game Maker, I use Clickteam fusion 2.5 (not that it matters, both are middleware engines lol) and the movement is custom so the bounce is programmed in there, it's a leftover from the design choice of keeping up the players speed. Originally the movement was way more floaty than it is now. I've minimized inertia a lot for the next build, I'm going to play around with the wall bounce and see how it feels. Going to rewrite this when I get time, hopefully solving things like diagonals being faster.
Hitpauses: The game currently pauses at player damage, critical hits and deaths. A buffer is going to be implemented so pauses only happen if there hasn't been one in the last 2 or 3 seconds. I might keep player pause permanent to keep damage communication clear.
Sharpie: I originally had an idea of him dodging if you aimed at him, but it was implemented so poorly, he just teleports away with no effects so it looks broken. I've remove this feature and also made sure he always damages you on attacks. I think you are the first one to actually figure out this was intentional.
Bullet in magazine: speaking of things that arent communicated... I have gears of war reloading in the game. If you reload, the reload bar will flash when it's half way through, if you hit R again it will give you 5 more bullets. Which is probably what you did by accident since I don't have any magazine upgrades right now.
Rapid P: I noticed in the video you said this was garbage haha but I think you figured out the point of it. It changes the gameplay completely. It forces you in close (Because of the short range), the insane rate of fire constantly refills your energy bar which lets you stay in baby mode. Honestly it's kind of the way I saw the game working in my head, but I'm also careful to not force this way of play onto the players. I really didn't imagine players staying away and taking potshots but I guess that's why people gravitate towards the sniper rifle.
Slowmo: good catch finding the little freebie period, a detail I put in there that people only notice if they play more than a round. Your idea of having one speed of slowmotion might be a good thing, I will have to think about it, it's quite a bit of a change from the original idea. In past builds you actually got a lot of energy back during slowmo but i actually made it small to add more challenge since it was possible to just stay in baby mode all the time.
I think you are on to something with the slowing everything down suggestion, maybe the floaty speedy player movement is too OP in its context. I'm going to try this out first before I start adding buffs during baby mode. The big pro I've always had is that your bullets dont get slowed down which allows you to deliver much higher amount of DPS than the enemies. Although I like the idea of cutting reloading.
The enemies bullets were significantly faster just one build ago, people still refused to use the slow motion haha.
In the video you also call the upgrades crap, they are mostly passive as you mentioned. I wonder if superficial upgrades that add things (drones, lasers etc) around the player are better?
For the next build I'm going to implement some of the above things, but also I'm going to nerf or maybe even remove the sniper rifle. It's not the main way I see this game being played. I'm going to try to make a weapon unlock system leaving Rapid P and Autorifle as the two unlocked ones, maybe it will force people to try new things. We'll see.
Great stuff my guy, hopefully you'll try the next build too!