Understand

Have you ever taken an online IQ test and then when the test was over instead of wanting to know your score, you were upset because they took your puzzles away? If so, then you are the ideal player for this game.
There are no instructions but it is easy to figure out what the game wants from you. Some levels will come easily and some will stump you enough that you'll need to come back weeks or months later. I wish certain levels weren't way harder than the rest, but maybe a different person would struggle with different ones.
I like the clean design with nothing extra or wasted. The sounds effects are perfect. No complaints.

Currently halfway through the game. Actual playtime is 19 hours; I accidentally left game on in the background overnight.

I like how individual puzzles are of medium difficulty and take about 15 minutes to solve, so I can play a puzzle during a short break. Chapters are independent of each other, you don't need to master one thing in order to progress. Level design is very elegant; I like how each chapter has the same number of puzzles and commits to its theme.

"circle to square... circle to square... circle to squaah, thats not a square."
"im just kinda drawing the line and hoping it - holy moly i solved it"
"not rule 1, not rule 1, not ru - THAT'S RULE 1??????"
"i understand it now! *draws line* ...hmm"
"three plus one equals four, four plus three equals seven, seven plus two... does not equal nine, apparently"
10/10 aha moments game

So, I have not beaten the game. I'm currently on 3-?. I can tell this is going to be a game I need to take one or more breaks on to complete, but I will say, I have gotten way more than my money's worth out of it. I think Understand is definitely not for everyone but for the right kind of person, this is something truly special.

I achieved 100% after 29 hours with looking up some hints and sometimes solving without realizing the rules by brute-force or just guessing.
I think some stages are not good especially the prime number level, it was terrible and almost completely out of nowhere.
Maybe you can think of this game as a riddle game more than a puzzle game; hence, the point of the game is to spot the rules, and there are almost no hard levels when you know the rules.
That said, most parts are great, I enjoyed it. Especially "think outside the box" levels, some of these are a bit questionable, though.
Overall, I can recommend this game if you are okay with doing some brute-force or if you love guessing.
Also, thanks to the dev for not making the game too lengthy and for the very affordable price!

A great game that scratches that rule-discovery and inductive reasoning itch. Sometimes frustrating (puzzle devs please stop making puzzles about the real-world time/date), but overall a very positive experience. Each world has some thematic consistency, although the specific rules within the world have some variety.

My brain hurts but it's surprisingly fun and high quality for such a minimalist game