No menu, no lobby, no daily-reward popup. Sudoku opens straight into a puzzle pitched at your level. Solve it, swipe up, and there's another one.
Most Sudoku apps make you shop for a puzzle before you can play one. This one hands you a board and gets out of the way. When you're finished — or bored — you swipe up and the next board rises from the bottom.
Every puzzle is graded by the reasoning it actually takes to crack. The chain of techniques a solver has to reach for sets the band; how much of the board starts filled in then grades the puzzle inside it. Ratings are built to move with real play too — as people solve, fail and skip, a puzzle's rating settles where it belongs. And the app quietly reads your recent solves and picks from the band around you, so the difficulty follows you up.
There is no hint button. Sudoku won't solve a square for you, and it won't nudge you toward the next move — the puzzle is yours. What it does do is take the bookkeeping off your hands.
Pencil in candidates as you go. Place a real number and it clears that square's notes and strips the digit out of every peer in the row, column and box.
Tap a digit once to hold it, then tap squares to drop it in — quicker than select-cell-then-digit when you're filling a run of the same number.
The number you're holding glows everywhere it already sits, and squares that only list it as a pencil mark are called out differently from the ones that hold it.
Each key on the number pad carries how many of that digit are still unplaced. When a digit is finished, the key says so.
Step back through entries, erases and note changes. Erase clears a square's value and its pencil marks together, in one press.
Leave conflict highlighting on and you get three mistakes, counted. Turn it off and the board tells you nothing until you're done.
Tap the timer and the board hides behind a cover that ignores every touch, so nothing moves while you're away from it.
Reset puts the givens back and clears everything else — entries, notes, undo history, the timer and the mistake count.
Park a puzzle mid-solve and it waits on the shelf with your entries, notes and elapsed time exactly as you left them.
A puzzle game lives or dies on how it answers your thumb. Sudoku answers on contact.
A 9×9 grid is a hard thing to hand to a screen reader. We did the work rather than shipping 81 unlabelled buttons.
The things most puzzle apps take from you, this one doesn't ask for in the first place.
There's a body of technique behind a stubborn puzzle, and it's smaller than it looks — two techniques finish almost every Easy board in here, and five finish almost every Medium. We write them up in plain language, on a real board, in the order worth learning them.
Sudoku is out on iOS and Android. Open the store for whichever phone is already in your hand.