5 stars: Ads don't interrupt gameplay. The hardest difficulty is appropriately challenging and can be solved methodically; it's incredibly relaxing for anyone who enjoys the comfort of simple arithmetic and logic puzzles. Also useful that they give you a single free hint each game with the option of watching an ad if you need another, which basically allows you to customize the difficulty level of each board.
4 stars: I love the logic puzzle of this game and am completely addicted. But a few things irritate me: It keeps prompting me to join events. I want a \
3 stars: Forced ad watching after each game in addition to banner. Premium is pretty cheap, but I don't like the app itself enough to pay to remove ads. On the one hand, it's well polished imo, but on the other, the way it handles mistakes (telling you immediately when you make one) can itself be used to solve puzzles. Also, make three typos and you have to restart the puzzle (though this can be disabled for some puzzles).
5 stars: Nice concept, perfect blend of sudoku and kakuro in one puzzle. If you're familiar with both, you'll make the jump to the expert levels in minutes. Very nice interface, minimal ads. Would love some more challenging modes though. I find it a little too easy to beat the hardest levels.
3 stars: I enjoy Sudoku and this game brings a slight twist to the gameplay, unfortunately the ad's are just ruining the experience, I just finished a game and had to watch 30 seconds of ad's then ...