Wow thank you for taking the time to play the game and for taking the time to write such thoughtful and kind feedback! I really appreciate it!!
To address some of your points regarding the UI icons and tutorial, I apologize for all of that! We were really pressed for time and we implemented the entire tutorial in a couple of hours, we didn't have time to make individual textures for each key/gamepad icon possible, so we just used a single standard "square" texture and pasted the universal icon for the "space" key as text rendered on top of it lol. We do intend to make real icons for everything though, and we'll be sure to make the icon for the space key wider for the sake of clarity!! The same goes for the entire tutorial part, I agree with all of your points and I despise text-heavy tutorials as well -- it was very much hastily thrown together, but we'll be sure to improve on it as we move forward!
Regarding your other points, don't worry I do not intend to dilute the game of its main focus at all! I don't intend for this to target the widest audience possible, and I am very much focused on trying to make sure that the core gameplay remains as satisfying as possible for anyone willing to learn how it works! That of course means that I can't cede on some things that would make this challenging -- I fully agree with you there! I do however think that there are some holes in this game currently that would get in the way of this, and would in turn make it just a tad more accessible for people.
For example, you could be a very good musician and rhythm game player, but if you have a weird audio device or a bad monitor, you'll inevitably have some nasty input latency that would mess up your timings. Usually, a good rhythm game has a calibration screen that would let the game mitigate and account for that latency so it doesn't feel nasty to play. This is something that we need and would make the game a tad more accessible without sacrificing quality. I also think that having multiple difficulty options with varying timing windows wouldn't hurt.
There are also numerous tricks in here already that make timing things easier (outlined in the game page). For example, even if you mistime your attack, the "impact" frame of the attack animation (the moment the attack lands and the boss flashes white) will always land on the next beat. So if, instead of focusing on the music, you focus on hitting any of the attack buttons right when your previous mistimed attacks land, you'll have a guaranteed successfully timed hit. Another trick is that the dash is free, so you could try to dash until you get it right, and when you do you'd immediately press attack or rewind or whatever you want to do and it will be successfully timed. These are all things that presently exist in the game but are not as intuitive as I'd like them to be. So I think it is worth investigating various different effects to get them to a more polished state (eg., via hitstop, particles, something else), which I think would make the game both more satisfying and more accessible without diluting it.
I am curious about what you mean by the "lock system". If you don't mind me asking, would this be different from what's already there? The game already automatically locks the camera onto the boss as soon as any boss fight begins.
Thanks again!!