That was really good!
I found myself enjoying the hex rotation mechanic a great deal. It's simple and satisfying with a good "first-level heuristic" so I can see how well I'm doing. It kept me entertained between the story bits. A solid entry.
Some things I think could be improved: (a) a targeting reticle would help. I know the hexes grew slightly when focused, but even a small, faint little dot would help me know where I'm focusing. (b) the movement, while deliberately slow for effect, felt like it didn't have to be as slow as it was. Rotating in particular felt like a slog. Perhaps a water slosh sound plus more bubbles when rotating would make it feel just as hefty, rather than slow?
As one last bit, I'm not sure if I "finished" the game at that last part. I unlocked that last room and then wasn't sure if there was more I should do.