This is a fascinating game. I picked it up after reading this thread and have been playing with it for a day or so. I’m a fan of games of this sort, but some of the levels really have had me stumped. It’s very much an “aha!” game, where once you get the key insight for the level you can normally work out the rest easily. What’s so impressive about it is that there are so many completely different “aha!” moments arising from such a relatively simple set of rules.
Those without self-control should skip this, but there’s a nice “spoiler-free” hint site that I’ve referred to once or twice. It doesn’t give the solutions, but it does a good job of nudging you in the right direction:
One problem I have with games like this, and I think this one is no exception, is that in the process of going through the levels you’re building up the skills and the mental language to tackle more difficult problems. That’s absolutely what you want to make a great game. But for me, if I step away from it for a period of time, could even be a few hours, I tend to have that knowledge erode. I’ve been stuck at least once because I didn’t remember a very basic thing from ten levels earlier, which I don’t think was really supposed to be part of the puzzle, it was a just a symptom of not being able to hold everything in my head at once for a really long period of time.
I had a very similar experience with The Witness – it was great working out the tricks, but unless you can access them all when you need them it can be frustrating. I’m fully willing to believe this is more of a “me” problem than a general one.