I enjoyed playing this game, the Cover Art Work would definitely make me buy this game when I had a NES!!
The controls for walking seems smooth, I could only observe a double jump issue, specially when you're passing through platforms pressing Forward and then trying to double jump at the same time.
I feel the music is some sort of loop, just being repeated, when I do OST's, I always loop, but larger sections of my own music , I always tend to start/finish with Drumbeats so that makes the loop easier to do, also, to make it feel more vintage, I get a square wave generator for each song 'voice' (each channel) and customize it until it looks appropriate for each section (Drums, Harmony, Bass and Lead). Another thing I like to do is to keep adding voices on the song, until all are playing together, and then finish with just the drum beats.
Another thing I would like to flag is that the character damage is not evident, when you take damage, the heart counter goes down, but, the character doesn't get 'red' or even blink, but that's just a minor detail and you can fix it quickly after the voting period.
Anyways, these are just minor adjustments, I see a good game here!!!!