It's an already thorough polished game. Not much I can suggest. Two things I might encourage to have another look at:
- The visual feedback of a tile being placed correctly was too subtle for me to realize. Only after a whole while I figured out that there is actually a difference in color indicating right vs wrong position
- The "success" audio feedback at the end of a level sounds kind of strange. But this might be because of my not-so-great loud speakers
Goot luck with the release! I assume game isn't far away from that, as the overall experience is already almost perfect.