Proven Sudoku
How to play
The rules are ordinary sudoku. The controls are built for one hand on a phone.
Step by step guides
Five tasks, each written out in order, using the labels the app actually shows.
- How to enter numbers and use pencil marksBy the end of this you will be able to fill a square, pencil in the numbers a square could be, and take back anything you did not mean.
- How to use a hint without spoiling the puzzleBy the end of this you will know how to ask what kind of step is available next, and what that does and does not tell you.
- How to check your work on a sudoku boardBy the end of this you will be able to find out whether anything you have filled in is wrong, and you will know what the check does not tell you.
- How to play a shaped sudoku boardBy the end of this you will have opened a shaped board, found out which rule it adds, and seen where that rule applies.
- How to share your sudoku resultBy the end of this you will have copied a result carrying your level and time, with a link that cannot give the board away.
Filling in the board
- Pick a difficulty from the home screen. Easy, Medium and Hard are three separate boards, each with its own timer and progress.
- Tap a number in the palette below the board to arm it. The number stays armed.
- Tap cells to place that number. You can fill every 7 on the board without reaching back to the palette between taps.
- Tap the blank palette entry to arm the eraser, then tap a cell to clear it. Given clues cannot be erased.
Pencil marks
Turn on Notes and your taps write small candidate numbers into a cell instead of filling it. This is how you record what a cell could still be.
When you later place a digit for real, that candidate is removed automatically from every cell in the same row, column and box, so your notes stay honest without any bookkeeping.
Undo and redo step through your whole history, including the automatic cleanup, so trying an idea costs nothing.
The timer
The clock starts when you open a board and pauses when you leave the app or switch away. It resumes where it stopped. Time spent away is not counted, and the clock cannot run backwards if your device clock changes.
Sharing your result
Finishing opens a panel with your time. Share it and the recipient gets a link showing which board you solved and how fast. The link carries your level and time only, never the puzzle or its solution, so it cannot spoil anyone.
When the next puzzle arrives
New boards appear at midnight UTC, and the home screen counts down to it. The day boundary is the same instant everywhere in the world, which is what lets everyone play the same board at the same time.