I think the gameplay premise is solid. If this was expanded into a full game past the jam I feel like it would be easy to implement more complexity and very interesting puzzles to make a pretty good game.
Viewing post in Felicity Flux's Lawless Laboratory comments
Suggestions? As far as what's here I'd say maybe halt all momentum when changing size mid-air because the jumps were a bit finicky at times.
As far as anything adding and improving things to make a bigger game (should you choose to do that) I can't really say anything specific. Just like any good puzzle game introducing new stuff like items, hazards, and mechanics in general as the game progresses to increase complexity.