This is just some friendly feedback I hope you don't mind.
The combat part should use some work (Of course this is a really early prototype) like directional shooting, 4 directions would be enough but 8 would be really nice. Maybe make the bullets consume less energy (Or give us more energy) so we can shoot more, even if they deal less damage it feels more satisfying (Think how people like to spam basic shot in megaman/metroid).
The spread shot didn't feel good at all since there is not a lot of enemies to try it and you can't shoot more than once. Aside from that, the platforms to jump higher (I think that's what they do?) felt more an obstacle than a tool since those jumps are just a little out of reach for the normal jump, I would suggest making the jump a lot higher or adding sound and visual effects to make the jump more noticeable.
The graphic aspect of the game is pretty much perfect for me, looks like a really well done Gameboy game and the music goes perfect with the ambient, I also would like to know the lore of the game eventually because it looks like you have a strong world building concept.
Overall I did enjoy the game for what it is (A very VERY early prototype) and I am sure it can turn into something amazing.