I love retro metroidvanias, this looks and feels phenomenal! I have not finished it yet, but I have some thoughts on what I've played so far
I will say that a couple situations feel like they need some slight tweaks. The flying enemies in the overworld in particular move unbelievably fast, there's no clear way to engage with them using the default gun other than sniping them from out of their range or gritting your teeth and taking the damage.
The high jump might need a quick explanation of its controls, though I was able to figure it out when I fell to the bottom floor. It also feels like the limited maneuverability of the high jump is just that way for the sake of itself, it seems to add more frustration to navigation than meaningful challenge to the game.
But all in all, it's really cool! I'll definitely come back to it and try to play it all the way through.