Really great work! Love the aesthetic! I fondly thought of Fireboy and Watergirl while playing. Your game is very cute and charming, and the audio + visual components fit together so well!
I ran into one bug on the level select screen: after beating level 1 and unlocking level 2, I couldn't select level 2 to play it, whether clicking on the play button or on the level background. I had to go back to the main screen and replay through level 1, then hit 'next' while still on the level 1 screen, to proceed.
Other than that, super fun (and challenging!)!