Hey, great game! I enjoyed the puzzle design a lot. I think you got some nice puzzles out of a fairly simple concept, which makes them feel smooth and elegant. I got stuck on one with multiple doors (where you need to stack the cube on the other cube, and there's the really tiny cube on the right). Still not sure what the solution is meant to be, but I had fun trying.
A few specific notes:
My highlight of the game's design was that I really liked that you gave us good reasons to switch between being large and small. I feel like often in these kinds of games, one or the other is advantageous, so one gets used way more than the other. Having the weight factor, or crossing large gaps, or shrinking to tight spaces, was a nice touch to make me want to grow and shrink regularly. If I had to give constructive feedback, I'd say I wish there was a little more interplay between the two (generally there were "now I'm small" puzzle elements and "now I'm large" elements, but I never got to a level that was "I need to be large, but don't fit. How can use being small to free me up to get large" or something like that. It's possible I just didn't get there, so a grain of salt), but generally I felt that both the small and large forms of the character were equally important to the puzzles, so way to go!
My low point would be that the surprise walls blocking the exit (or some other important path) when you activated a switch felt a little unfair. I had no way of knowing they were there/what they'd do, and then I'd have to play a level multiple times just to get all of the necessary information to solve it. I'm sure the longer and more complicated a level is, the more frustrated I'd be at the hidden information. Maybe some visual cues of what does what would alleviate some of the tension.