Native Sudoku: Touch, Keyboard and Pencil Notes
The Sudoku page and homepage use the same native board. On a touchscreen, select a cell and press one of the numbered buttons below it. A phone typing keyboard is not required. These are the implemented controls, not a claim of testing every phone or browser.
Select the cell before entering a number
Given digits are fixed. You can select one, but entering a number will not change it. Start with a cell that was empty when the puzzle appeared.
| Action | Touch or pointer | Keyboard with a board cell focused |
|---|---|---|
| Select a cell | Tap or click it | Move the selection with arrow keys |
| Enter a digit | Press a numbered button | Press 1 through 9 |
| Clear an editable cell and its notes | Press Erase | Press Backspace, Delete or 0 |
| Switch pencil mode | Press Pencil notes | Focus and activate the Pencil notes button |
| Restore a previous entry or note change | Press Undo | Focus and activate Undo |
Arrow keys use a wrapping index: Right from column 9 selects the next row’s column 1, and the last cell wraps to the first. They can select given cells too. Number and arrow shortcuts are handled on board cells, not globally while another control is focused. There is no letter-key shortcut for pencil mode.
Try the note controls
Use any empty, editable cell. The numbers below demonstrate controls, not that cell’s solution.
| Step | Expected result |
|---|---|
| Turn Pencil notes on and press 2 | A small 2 appears as a note |
| Press 2 again with Pencil notes still on | That note is removed |
| Add notes 2 and 7; turn Pencil notes off and enter 4 | A normal 4 replaces that cell’s notes |
| Turn Pencil notes on and press 2 in the filled cell | Nothing is added; notes require an empty cell |
| Press Erase | Its entry and notes are cleared |
| Press Undo | The previous entry or note state is restored |
Notes are manual. Placing a digit does not remove matching notes from neighboring cells or calculate their candidates. Recheck notes against the current row, column and box after other entries change. Solving basics explains the reasoning.
When an action seems to do nothing
| Symptom | What to check |
|---|---|
| A selected digit will not change | It may be a fixed given |
| A small digit appears instead of an answer | Pencil notes may still be on |
| A note disappears when the same number is pressed | The number toggles that note off |
| A number key does nothing | Focus a board cell; shortcuts are not global |
| Undo is disabled | There is no entry or note change left in this puzzle’s history |
| Check reports no incorrect entries but blanks remain | Filled answers match; this is not completion |
Check compares normal entries with the stored solution. It ignores notes and does not supply hints or deductions. The answer-check example shows a wrong digit that has no immediate duplicate.
Before refreshing or switching pages
There is no resumable game save. A reload or leaving the page loses the current board. Keeping a tab open retains progress only while its browser runtime survives; a browser or operating system can discard and reload a background tab. See the session table for Restart, New game and cancellation.
JavaScript is required. If a control fails, report the Sudoku issue with the page, browser, device and action that failed.