Very cool game and well polished! You nailed the presentation.
As a suggestion, some of the collision rects feel a bit aggressive to me, or maybe it's the player is slightly large. I'm not certain, but the collisions sometimes feel just a pixel or so off from what I'd expect.
It's also frustrating to have to start from the beginning when you run out of hearts. A checkpoint system, or even just leaving the level as-is and going back to the beginning would be a nice feature when dying so you don't have to repeat areas.
Overall, though, it's an excellently made game. Well done!