very fun! i genuinely got sucked in and comleted all the levels at like 3am. most of the upgrades are very nice quality of life things, i like how you progressively unlock them as you get onto more difficult puzzles, it keeps the difficulty paced well.
the one upgrade im a bit less sure about is the auto rotate one- it does make the puzzles easier which is good, but the concept of rotating puzzle pieces is one i havent seen in puzzle games before and it's kind of sad that you only use it for a few levels before you buy the upgrade