Functional. Hard. Not the best aesthetics
Now the middle-ish news. These puzzles are hard. There's no real difficulty curve. For experts, this is a good thing, but beginners should stay away.
Now the bad news. The visuals are a bit TOO fancy. Fancy visuals are for action games; for puzzlers like this, function trumps form any day. This may sound like a silly complaint, but when all you need is a square and a dot, getting creative just feels weird.
THE VERDICT: It's worth the price tag, but better apps exist.