I'm really sorry, but having to start over every time I get hit by something is just what makes me not wanting to play the game at all. I really had to force my self not to quit after 2 deaths, got to around I think level 5 or 6, and just quit after getting KO'd twice by unforgiving hitbox of the red monster with wings. If you're going for the grid-based look, maybe make the hitboxes of everything grid-like too, even if you want some characters to be larger, make them larger by the grid not like 1,5 of a block or something like that. I personally didin't like that my Character was 2 blocks or maybe even a little more, but that can be attributed to just preference.
And one more pretty brutal hit from me, so I'm really sorry, don't want to attack or discourage anyone but... If you want to go with graphics changing back to how they used to be, maybe it would be better to start with more up to date graphics. I didn't notice any change in my playthroughs until I checked it in the "in what way does your game fit the theme?".
I really liked the music, together with the visuals of the monsters it gave a pretty creepy vibe, so if you would make a horror game with those assets, that would probably work wonders.
Consider making the game much, much more forgiving next time, especially for a Game Jam, people are going to stop playing really fast when you punish them so hard.
Anyways, good luck in both this and any future projects.