How to play / Enter numbers and pencil marks

How to enter numbers and use pencil marks

By 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.

Before you start: A board open at any level.

Steps

1. Tap a number in the palette along the bottom to arm it.
2. Tap any empty square to place that number.
3. Tap "Notes" to switch to pencil marks. The board confirms with "Notes on: taps pencil a candidate".
4. With Notes on, tapping a square pencils the armed number in instead of placing it.
5. Tap "Notes" again to go back. The board confirms with "Notes off: taps place a digit".
6. Tap "Erase" and then a square to empty it.
7. Use "Undo" and "Redo" to step back and forward through your moves.

What happens

Placing a number clears that number from the pencil marks of every square it can see, so the grid tidies itself as you go. You never have to rub out a mark by hand because a placement made it impossible.

On a keyboard

Arrow keys move around the grid and 1 to 9 fill a square. Backspace, Delete or 0 clears one. N switches pencil marks on and off, and the usual undo and redo chords work as they do everywhere else.

If something goes wrong

Tapping a square does nothing

No number is armed. Tap a number in the palette first, then the square.

Taps are pencilling instead of placing

Notes is on. Tap "Notes" to turn it off and the board will say "Notes off: taps place a digit".

You want to start the board again

"Clear all entries" removes your entries. The app asks "Clear the board?" first and tells you that the timer keeps running and the board stays the same one everyone is playing today.

Related

• 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 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.

What this is for: read about the feature.

Last updated 2026-09-20.