It's an okay game, but pretty basic. The things you have to avoid come pretty slowly and often it obstacles are clustered in two lanes while one remains wide open so you can just sit there with no risk of hitting something. The different hazards sliding around would probably feel a lot more like music if you had some kind of guide lines indicating which quarter/eighth note they were inside of. That, plus a more aggressive layout of hazards, could force the player to tap along to the beat. Finally, some kind of pulsing from the sprites is a great way to immerse the player in the music. Right now I can imagine it would be pretty easy to play this without sound at all, which is never a good sign for rhythm games.
Balance-wise the ability is kind of weird. I used invulnerability a couple times and restored a heart like once, but since the game is pretty easy these mechanics mostly went unused. There's one really hard section near the beginning but the rest is all pretty easy to do without hitting a hazard at all.
The graphics (specifically the player) are cute but get old very fast with basically no background and only four sprites (player, two hazards, carrot.) The song also feels longer than I would have liked. For something short like this, it might have been more fun to have three 1:30-2:00 songs with varying difficulties.
Technically speaking there are a handful of bugs involving things that should be deleted (the heart and transition animation.) Are you trying to use unloadMovie on these objects? Ruffle doesn't support these yet, so you have to swapDepth to a positive value and then call removeMovieClip.