Very neat! A nice chill experience.
+ Cool visuals. I'm particularly fond of the aurora effect.
+ The choice of music is a solid fit
+ Straightforward gameplay loop that works well
- I wish there was a bit more interaction I could do. You're working with only 3 buttons, it'd be nice if there was more to do with them.
- There's not much graphical indication of what's happening. I don't know how many particles I need to collect to advance, and the train doesn't really announce itself, so if you're on the right side, you get no warning.
- I found a fun minor bug that's potentially a softlock: Collecting particles as they bounce will lift your character off the ground. While lifted, you can duck the train to remain in midair. If the train hits you in this state, you can no longer climb back up, and the particles eventually gather on top of the train where you can no longer collect them.