Ignoring the more obvious things that need work, that I assume you are aware of, I love the concept! Using the size changing mechanic to navigate a puzzle platformer is wonderful fit and has a lot of potential! And the art style on the backgrounds looks incredible! If you polish it up, give it more of a story to explain the size mechanic, and give it either add in more combat or more puzzle mechanics (depending on what you prefer), I think you could have something special.
- Jesse