Hey, pretty promising! I love me a good beat-em-up and this definitely had a lot of good points to it. Neat animations, tons of cool moves to use on enemies in stylish ways, satisfying feedback from attacks, good PS4 gamepad support, and so on.
Having said that, though, I am a lover of beat-em-ups and so I gotta be harsh on this with feedback so hopefully it becomes great in its final form. I might be going overboard with some of this stuff as its tough to tell what you already know you need to do since it's just a prototype, but here we go:
*Tutorial was kinda bad in that it throws way too much information on you and I could barely remember it all. Don't get me wrong, some of it is intuitive in that it uses rather universal controls that a lot of other beat-em-ups do, but it also had a lot of wacky stuff that flew right over my head. If I had my way, I'd like it if the tutorial was separated into bite-size sections: basic movement, basic combos, special moves, grabs, etc. Also it'd be great if you could actually control and participate to build muscle memory and learn by example. Also it'd be great to have a move list to quickly reference at any time, like in a fighting game.
*There were some wonky control issues that made moves come up when I didn't want them to. The biggest issue was running: you should only initiate a run when you press the same movement direction twice in succession! In this demo, it was possible to run by pressing two different directions quickly, when constantly screwed me up. Basically, you should only run when you quickly press left+left or right+right, don't run when you press left+right or right+left.
*The enemies were incredibly boring and brainless and lacked any sort of variety or threat to them. Sure they were kind of fun to beat up like sandbags at first, but it started to get real monotonous really fast. Changing their colors and giving them more health and just increasing the amount of them doesn't make the game fun: I need enemies with different attack patterns to contend with that really make me think, improvise, and crowd control. You know, maybe get some jumping enemies, some grabber enemies, some fast enemies, some projectile throwers, whatever it be. Quality over quantity is the goal here. Without that I can't really get a feel for whether the combat is any fun in the long term.
*The fact that you couldn't go up or down in the space felt very limiting: usually beat-em-ups are 2.5D and have a great strategy to them where you need to use the whole space to crowd control: moving around to dodge or herd or control enemies. Don't get me wrong, 2D beat-em-ups can work, but this game didn't really show me it working at all: as said, the enemies were really brainless so all you had to do was just punch left and right and that was it: felt like there was no strategy to be gained, though if you vary the enemies to make up for this and work with the 2D space, then it would be fine.
*There were a coupla cases here and there where the game just felt kinda wonky, like maybe my punch hitbox being a bit shorter than I would expect, and the ground pickups being offset so much it looks like I shouldn't be able to pick them up: just subtle stuff like that, hard to explain it all.
Best of luck on working on this: love me some beat-em-ups and I'd love to see this become great as, while I do have some complaints, I think it has a solid foundation to work from!