It looks and plays great!
Not that I can do a lot currently, since I can't guess which code fits which door, and some of the numbered rooms do not have scrolls yet.
Can you try give a bit more information about the codes and doors in your final version? Preferably on the beginning of level 1, so that people know what to go for. Or ask people to go to level 4 first. (If I remember well, you should start somewhere in level 4, as the original game also started there.)
And if I can add another suggestion, can you please explain in your final version a lot more about
1) what those yellow bars near the orbs mean
2) what you mean with the numbers on the scrolls (for example, I still do not understand what sequence mean, or the green numbers in the rooms)
And yes, I have already read many scrolls in level 4, but I still do not understand, maybe because english is not my first language... The challenge should be in getting the scrolls, and not understanding the scrolls.
[ I will not test this hold yet, as I can only understand how to open that first one in level 4. Although it looks pretty solid. ]
I also noticed that some of the rooms are one way only. If you leave it from one way, they you can never return (except by saving). (I can't remember having one way rooms in the original metroid.)
I am really looking forward to it! It looks great! Please finish!
-- Tim