What is Sudoku?
Sudoku is a placement puzzle. You begin with a partly filled grid and use the given numbers to determine the empty squares. There is no arithmetic: the digits act as nine distinct symbols.
Rows, columns and boxes
The board has nine horizontal rows, nine vertical columns and nine bold-bordered boxes. Each box contains three rows of three cells. Every row, column and box must contain each digit from 1 through 9 exactly once. Starting clues stay fixed; each Puzzuno puzzle has one solution.
Use pencil notes
Select an empty cell, turn on Notes and enter the digits that could fit. Tap a digit again to remove its note. A number you place removes that candidate from the other cells sharing its row, column or box. Undo restores those notes along with the previous number.
Your first deductions
Begin with a nearly full row. List its missing digits, then check the columns and boxes crossing its empty cells. If only one digit can fit a cell, you have a naked single. Next, scan a whole box for one missing digit: if it can go in only one square, that is a hidden single even when the square has several notes.
Keep alternating between rows, columns and boxes. After placing a number, check its neighbors again. If you get stuck, pause or use a hint. Looking away for a moment often makes a missed constraint easier to see.
Choose your difficulty
Easy offers more starting clues and favors straightforward deductions. Medium asks you to cross-check more rows, columns and boxes. Hard and Expert offer fewer clues and more demanding combinations. Difficulty varies between puzzles, but every Sudoku has one valid solution.
Keyboard and touch controls
Click or tap to select a cell. Enter 1–9 with your keyboard or the number pad. Arrow keys move selection, N toggles Notes and Backspace or Delete erases an editable cell. Undo and Hint have their own buttons. Bold digits are fixed clues; lighter digits are your entries. Underlined digits with an exclamation mark are incorrect.
Frequently asked questions
Does three mistakes end the puzzle?
No. You can keep trying. Mistakes count incorrect entries, not incorrect notes. Undo changes the board but keeps your mistake and hint totals, so the final summary reflects the whole run.
What does a hint do?
A hint fills the selected editable cell with its correct number. If that cell is already correct, it fills another unresolved cell. You can undo the fill; the hint still counts as used.
Can I leave and return?
Yes, when browser storage is available. Moves save immediately and the timer saves regularly. Pause stops the timer and hides the board. Leaving the page pauses play; reopening a saved puzzle starts paused so time away does not count. Progress belongs to this browser and device.
How do daily replays work?
The Daily Challenge uses your local calendar date. Everyone choosing that date gets the same Easy Sudoku. Your first completion can earn the daily bonus and qualify your streak; subsequent practice completions do not grant the same daily rewards again.
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