I love this so far.  It's really polished.  I haven't finished it but probably will come back.

Very promising metroidvania! I could tell the inspiration from Cave Story right away. If you do some tuning to the controls, it's good to release. 

I love this. It feels like an adorable love letter to Super Metroid; the broken lab containers, crawling spikey enemies, and you even nailed the isolated rainy atmosphere of the surface of zebes! My overlying problems with the game are with the controls. The high jump is a bit awkward to use, compared to the rest of your smooth movements. Needing momentum to move with the high jump properly makes platforming difficult and tedious. Also, you forgot about the select button! Using metroid two which was on the gameboy as an example, you could swap between missiles and your normal gun by pressing select.  (On keyboards, select is usually mapped to the shift key). Being able to swap weapons like this would make gameplay even more crisp. 

Nice little metroidvania! The soundtrack if very good! Well done!

PS: Feel free to try my game out! Cheers!

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.