Played qop 1, really enjoyed it, now played qop 2, and it was also a lot of fun. There were definitely some more challenging puzzles (and to be honest a few of them I ended up searching the Internets for solutions, but I'll probably come back at some point after I've long forgotten those few and play straight through without any assistance / help).

The qop games so far (1 & 2) have been mostly satisfying. I think a big improvement would be the use of the Escape (ESC) key to bring up the Menu, so players can exit the game using standard key mappings. Other than that, its hard to find anything critical or what could be improved, a tough puzzle is just that - a tough puzzle, and shouldn't factor into a recommendation or a review - and I was able to solve most of them on my own.

I hope there is more coming in this IP, Quiet River has something here in the hypercasual space. I haven't checked to see if its available for mobile devices, but I could imagine this being played a lot of players on those devices.