Really nicely done! Great polish for the short time period, little story elements and all. Fun way of jumping between the sections too. I have to say, adding the little secret keys was a really cool way to let me manage my own fun levels - going for the extra reach when I had the motivation, but then focussing on just the obstacles when I was getting towards the inevitable end of my play session.
Main point of feedback: I was having a though time making some jumps from ramps after speeding up. Intuitively, I wanted to keep pressing in the direction I’m going after doing the charged speed boost, but it seems like applying my own direction to that would cancel the extra interia, nerfing the boost, and I was never too sure when I could start taking over again. That had me stuck in one section, and based on the screenshot of the overall level loop (which is super slick btw), I probably only got something like a quarter of the way through.
Edit: Almost forgot, but the little tactile sound of the clack of the marble landing was sooo good, good touch.