Cool implementation. Event tough i saw few other games with similar sizing mechanic, this stood out a lot for me. The art, visual representation and atmosphere was cute and playful. Even if some levels were simple it was still enjoyable and relaxing experience.
The only suggestion i could give you is that we need more levels or more complex ones. Something like where you force player to choose right size in mid air, or have huge drawbacks for being in bigger state. Or have different approaches to solve the same level. Basically adding some variety in levels and how mechanic can be used would make it an awesome game.
Overall, for a such a short timeframe it is an impressive work, I enjoyed it!