5 stars: I have played all of the Bonte color games, and liked them, so I thought I would try this one. Overall, I liked it. Some levels were super easy, while some were fairly challenging. One or two made no sense to me, so I had to cheat and look up a solution. I like that the ads are not obtrusive, and only play when you ask for a hint. Good game.
4 stars: Puzzles are about discovering the mechanics specific to that puzzle. It's mostly done well, though some concepts repeat a bit too often for my preference. If you've played any of Bart Bonte's other games, you know what you're in for. There is one major drawback for me; sliding tile puzzles. They feel like a departure from the discovery style of the other puzzles. They were a frustrating disappointment every time they came up.
4 stars: Very nice game. Not plagued with ads. Like red, yellow, or other games. Hints not terribly useful. Overall solid and worth getting. spoiler below. Was completely stuck on level 14. it says follow the symbol. looked through reviews to find answer - who draws a 6 like that? given that you could start from anywhere, it feels too random. Minor nitpick in a fun game.
3 stars: It's too much fun. But sometimes ads do play between levels even though dev said they only play for hints.
2 stars: Some of the puzzles are pleasantly challenging, but others can wind up being needlessly repetitive. Also, way too many sliding-tile puzzles; after the first (not counting the trivial 2x2 ones) ...