Congratulations on your game! It's a very challenging platformer, especially with the world-switching mechanic.
One suggestion is that instead of resetting the music when switching worlds, you could have both tracks play simultaneously, one at zero volume and the other at high volume. That way, when switching worlds, you just invert the volume; the one that was high goes to zero and the one that was zero goes to high. This helps avoid repetition and also gives us the chance to listen to the music until the end. We did this in my game, as it has a similar mechanic. Congratulations. Your work is very good.