4 stars: Some good logic puzzles, and mostly a good interface. The one thing that's really missing is some sort of "check your answers so far" feature. It has a hint feature that gives you free answers.... But I don't want free answers so much as I'd like to be able to confirm that what I've filled in so far is right. Especially for complex puzzles
5 stars: If you want a number of interesting and fun logic games, step right up. This is for you. However, if you're not an afficionado, it may be more frustrating than it's worth. Tutorials are just okay, and for some games just aren't enough. Some games would structure puzzles to introduce you to concepts that they would make you demonstrate in order to proceed. This game doesn't. There are lots of solving techniques that just aren't explained and that you probably won't come close to finding on your own. See Minesweeper. Everything can be achieved without guessing, but the process of doing that is far, far more annoying than it should be. However, that's not the *fault* of someone meaning to collect puzzles. It's just that the game would be exceptional if it did.
5 stars: This is a great app! All of the games are designed to make you think, and they definitely do that! The only thing I can think of that I would like to see is an explanation with the hints, so we can see WHY that symbol goes there rather than just filling it in, because the entire reason I love these kinds of games is to follow the logic all the way...