It's weird, I had no expectations but felt disappointed at first by the demo. I think it's like I was expecting "more" than Metroid, which is kind of silly of me because it's advertised as "Mini" troid. It delivers all the basic gameplay pretty well and plays and handles pretty much like a 2D Metroid game, so I can't really fault it there, and as I played more I got into it, but I kept running into a LOT of low framerates, even in empty rooms.
I really want a map. I got lost
I see two "fuck-you" points in the green area, also. When traversing along the upper-right tunnels towards the boss there's a place with spikes below and a man-eating plant above. I see no possible way to avoid the plant, so I have to get hurt and use missiles every time, and there aren't many opportunities to recover health or missiles in that area. As well, my strategy for getting through the eye-door to the boss was to stand there firing and soaking up hits, because it looked impossible to shoot at the open eye without taking damage. The boss himself wasn't nearly as bad, after a few tries I got to "homeostasis" and then it was just a bit repetitive.
Anyway, best of luck getting it to completion