I went in a square and left as so much more!
I really liked this game. It's unique and was satisfying to play. I had fun working out how to acquire the shapes (especially the last few), and using them to move along walls was really appealing in an old childhood-playing-Tangrams kind of way—also the morphing animation was satisfying especially when it happened that there was a flow of one shape to the next without needing to reposition.
It's funny to me, the control-scheme feels like one a vim programmer would come up with ^_^. I thought it worked pretty well, though I did keep finding myself wanting to switch to the arrows for the placement step instead of continuing to hit the same shape number.
I kind of agree with Cormorant that the visuals were the weakest part of the game. I wasn't bothered by them, but if there was a place to improve, that would be where I would start.
This is one of the few entries where I actually wish there a little more to explore. So many metroidvania's suffer from lots of filler rooms and areas that either just get you from one place to another, or are just there to make the experience feel vast. I love that every tile in this game is necessary and serves a part of the puzzle, I would definitely have played more without getting bored!
Overall, a stand-out experience. Great job!