Very sweet game! The art was incredible, very detailed, and the whole world felt just amazing. It was a unique way to use sizes, not just size up or size down as other games did. The challenges were great, and the introduced mechanics were really interesting and added depth to the game.
Overall, I enjoyed it and the game felt great! If you decide to continue I suggest a bit of improvement on movement since it felt a bit floaty, especially on jumps.
Also, I feel like blur or a bit more dull colors on parallax in the background would really make the whole game pop up even more (don't take it too seriously since I am not a visual artist it is just a thought :D) Even though art was gorgeous on its own, I feel like making background details less visible might be worth to try out.
Well done on your game, it is definitely a creative approach and a strong entry!