Great idea for a puzzle platformer. I didn't expect there to be such a focus on dexterity, since the screenshots made it look like it was going to be more of an abstract puzzler. That's not necessarily a bad thing, but there were a few funny moments I had:
1) I sometimes had to tiptoe on the edge of a platform as much as possible before "puffing up" so I'm not sure if that's in the spirit of what your vision is.
2) In order to get a good platform in midair, I often spam-pressed the expand key while letting the block fall a few pixels at a time to try to get the optimal placement. Again this seemed to depend more on dexterity than abstract problem solving.
3) Sometimes I wracked by brain for a clever solution but it turned out I can just jump over normally. It wasn't very obvious to me what the limits of jumping are (it's obvious in the vertical direction but hard to judge whether you can make a long jump or not).
As a contrast I think the main mechanic in level 4 was much more aligned to the puzzling aspect.
If your intention was a dexterity-based puzzler from the get go, then please stick to your vision. I just think that presently there are some awkward tensions between the abstract part and the dexterity parts.
Great game overall!