I hate that I didn't like this because I really wanted to like it, but there's just so much wrong with this game. Although the music and aesthetics are great, mechanically, this game is in shambles. The two biggest issues I see are the fact that the hitboxes, especially for the main character, are very off. I've taken damage from things that didn't visibly come into contact with my player sprite. I suspect this has something to do with the fact that this was made in Pixel Game Maker, and although I know nothing about that engine, I feel like the dev may have made the sprites for the player character too small for the pre-made hitbox.
Furthermore, unlike almost every other game I've ever played, this game has no invincibility frames. So when you get hit, you'll just keep getting hit until you die. When you combine it with the fact that the game is very fast and a bit slippery, a lot of the deaths feel unfair. It was very easy for me to end up at 1/4 HP on the 3-screen walk to the boss because of these issues, which keep in mind, didn't go away when the boss fight started, so I would quickly take damage from something that didn't touch me and i would get re-spawned.
If you wanna hurt yourself, go ahead and play it. Otherwise, there's better metroidvanias.