Oh I like this. I had a smile on my face through my entire playthrough. The whole presentation feels so polished and professional. My favorite has got to be the animation on the checkpoint - it feels like a balloon and I love it. The ending was adorable, and the art piece shown afterward was made me smile. I'm sure I would have enjoyed it even more with a controller, but I played with keyboard and mouse and still had a great time. The camera tweening makes it feel like this is an intended way of playing, even if its not *the* intended way of playing.
My one suggestion is to maybe add a blob shadow directly below the player and floating platforms to help with depth perception.
Overall, this was a great time, and I can't wait to see where you take it next.