Ninekeep: Sudoku

Ninekeep builds its puzzles on your device now, so boards stop running out and the daily never comes around a second time. Difficulty means something specific too: Hard and Expert boards now genuinely need the techniques those words imply, rather than just showing fewer numbers. There's a second way to play. Sums boards start with no given digits at all. The grid is drawn into cages instead, each printed with the total its squares add up to, and you work back from the arithmetic. It's the variant usually called Killer Sudoku. Four difficulty levels like the classic boards, and its own set of best times. Hints teach now. Instead of just filling in a square, a hint names the technique it used, shows you where to look, and explains the reasoning. It still won't tell you the digit until you ask it to place one. There are thirteen techniques it can teach, up through X-Wing, Y-Wing, Swordfish and Colouring, and the app keeps a record of the ones you have solved with unaided. The first two hints on any board are free, the way they always were. If you want another after that, you can watch a short video for it, or turn ads off for good with a one-time purchase in Settings. Saying no to the video leaves the board exactly as it was, and there are no ads anywhere else in the app. Your Ledger now syncs between iPhone and iPad through your own iCloud account. There's no account to make and no server of ours involved, and if you aren't signed in to iCloud everything stays on the device and works the same. There's a widget too, for the Home and Lock Screen. It carries your streak and whether today's board is sealed yet. Pencil marks can fill themselves in, if you would rather not transcribe them by hand. They are only ever the candidates you could have worked out yourself, and they tidy up as you place digits. One undo takes the whole thing back. Solved boards now earn Marks, which unlock things in the Bindery. Marks are earned by solving and by nothing else. They cannot be bought, and they cannot buy hints, streak repairs, or anything that touches the board you are on. The four themes you already have stay free. If you broke a streak by missing a single day, the home screen offers it back for one video. It covers one missed day only, and only the day after. The ledger fills in backwards now too, so a day you missed entirely can still be sealed later. You can hide the timer, if the clock was the part that made it feel like a test. And you can start a board by asking Siri, or straight from Spotlight. — John