This is an excellent entry, as you're well aware. Good work. A full, playable game with original art and music. Quality stuff. You've already got a lot of great feedback so I'll try to focus on things others haven't mentioned:
1. There's no autosave after you beat the final boss; During the escape sequence I missed a jump, ended up in an entirely different area, and had no way of getting to where I needed to be except backtracking all the way around. Before I got there I died and found myself having to face the final boss again. Aaaaaaaaaaaaaaaaa. Maybe I'll try again later, but I don't know...
2. I *really* wish saving would refill health, at least before the final boss. I found myself going in with 50 health and no vials in sight. The final boss was pretty good--challenging and intense--once I realized how it worked. But it was way harder than I anticipated bc of the save issue and because I foolishly did not get enough bomb upgrades.
3. I quit this game and picked it up again several times because I kept getting stuck. For me, the environmental instructions were a little too subtle. It began with the first boss after getting bombs. The bomb targets didn't really look like targets, and even though I blew up one, nothing happened. It didn't occur to me that I needed to find and blow up all of the targets in the area to get out of the room. I thought it was soft-locked. This happened again after getting the whip. There was so much going on in that chaotic miniboss room I had no idea that I just had to keep whipping the thing over and over again and causing the miniboss to keep getting zapped. And again I was confused with the final boss, though by now I had kind of figured out how the world worked and figured it out without too much trouble. I think one thing that would help would be showing the player a more immediate connection between cause and effect in simple rooms, and be a little more obvious with player feedback.
4. I think at times the level design did not live up to the potential of the mechanics. Large sections of the game felt like "homework" jobs, like 1. collect bombs, 2. bomb targets, repeat. Some of that is not bad, but at times it felt a little tedious.
5. I like the aesthetics a lot but it could use some variety.
Overall I think it's a quality game, definitely one of the best entries, and I hope that some of the issues people have raised get addressed, because it's nearly there.