Nice job on the game. :) I love the art and the controls feel nice. The stars and notes were confusing. They felt like collectibles, probably because of how they were placed along the path at times and others just out of my reach so that I'd have to actively try to obtain them. Not sure how you'd get around that if you didn't want to make them collectible. However I would suggest making them collectible as that could easily add some dopamine to the gameplay with some lil bling noises.
Rather than starting the game on a timer, I would suggest starting the game when the player presses a button. This allows them to sit and take in the environment, which I often like to do when I first start a new game / level (level not relevant for this game given its nature, but for future references).
I felt a little uneasy from the movement, and I'm not really sure why. It might've been the fast paced camera scrolling. But I started to feel a little motion sick pretty quickly when it started and afterwards felt slightly dizzy. Not a big issue for me, but for someone more prone to motion sickness it might be a bigger issue.
The falling platforms don't stand out enough from the normal platforms. I even had to ask myself "right, so why do these platforms keep falling" before I realized they're somewhat dark. Which I don't think stands out enough for the mechanic. And also the falling platforms didn't impact gameplay at all since by the nature of the game I wouldn't be staying on them for long and ideally moving in one direction constantly.
There were jumps occassionally that felt pixel perfect. Like I needed to jump at the last possible second to successfully make. This was made worse due to the fast movement, causing me to not realize that I needed to make a pixel perfect jump fast enough. Though that could just be a lack of skill issue, but it made my death feel as though it wasn't my fault.