brooooo i LOVED this game.
I refreshed the browser page like 12 times bc i thought the game bugged, i did not wanted it to endo so soon lol.
Some things i think you should consider adding are:
-add infos of what each weapon update
-add a better options menu, where you can change the volume of music and the sfx it self. I personaly play those indie games while watching movies or series and the game music annoys me when it blends with the movie music and the voices.
-add some more items and power ups to the game
-i dont know if it was a feature that you planned, but when you exit a room, your hp gets full. it makes the game very easy and it makes the heath item uselles and annoying when you are farming coins and it drops hearts.
-Make weapon upgrades more impressing, maybe adding combos or different attacks, like a down + attack
-add a bow and maybe a shield to the game
Other than that i think the idea of the game is amazing and you did it very well. I hope to see some more updates on that and if you are making this game alone and want someona to test the game and provide you feedback, feel free to contact me!