Level 19 felt like it needed pixel and frame perfect inputs (although I beat it eventually) unless I was doing something wrong.
I found a couple weird things with the level select menu, if you press z it resets the scrolling background to its initial position, and if you press r it reloads the menu. Also, after exiting after getting to level 19 from the start, the level select screen would permanently not let me go to level 19, but would let me go to other levels including later ones when I unlocked them.
Secret frog dance would have been even cooler if aligned with the music rhythm.
Great game though. Loved the ending. Frogs are cool.