Hey, thanks for the feedback!
In response to "jump height, crouching, traversing the world" - You got that pretty spot on based on how I want the game to feel. :) And yes, the inspiration from metroid is obvious, I'm definitely not hiding that. I want it to feel as much as a metroid game as possible.
Yeah, the music is very much work in progress at the moment so that will definitely improve at some point.
I'm planning to update the demo very soon(tm), which will include lots of sprite updates among other things. Hopefully that will improve most of what you were thinking of.
Anyway, glad you like the game. ;)