So I spent time on this game last week and it turned out to be a bag of joy. A varying degree of vexation, but oddly captivating. With limited time I only managed to clear enough levels (all of my present unlocked sets have at least two or three unfinished levels sad to say) to unlock the next set of puzzles.
(Oops! I'm supposed to post this in the original thread. Forgot I'm actually viewing the discount thread!)