After trying nearly all of the free sudoku apps, I have rested on this one as my favorite for actual game play. The puzzles are well-designed, and even the hard and expert puzzles are actually solve-able without notes or hints if you’re good enough. That said, it is not without its faults. I don’t mind ads, but they are a little excessive, (and it is a bit jarring to see somewhat threatening NRA ads constantly). And frustrating that the clock starts on your game while you are still in the ad. The timer works fine on individual games, but the app does not accurately compile data for you to see if you are beating your own times. The “winner” screen is visually and functionally buggy and pretty useless. Despite all of this, I still play it daily for the good games. Though I imagine there will be a day when one too many NRA ads send me over the edge and I delete it forever and go buy a sudoku book.