This is super neat! The gameplay feels so smooth, but at the same time snappy enough for a platformer. Really love the whole atmosphere: the colors, the particles, the music. I often feel kinda stressed by platformers, but this one had a calm and cute feeling to it. The gameplay itself is kinda hard at some points but still perfectly possible.
Edit: Oh wow, you did EVERYTHING by yourself? That's impressive. It all fits together quite perfectly!