The game guide
Free online sudoku in the Sanctuary of Nine
The Sudoku turns a familiar number puzzle into an expedition through a celestial sanctuary. The glowing board, floating particles and musical feedback accompany your progress, while the puzzle remains a real sudoku: observation and deduction come first. Play for free in your browser, on a computer or phone, and continue from one completed grid to the next. You need no mental arithmetic, just a way to work out which number belongs in each cell.
Sudoku rules: rows, columns and 3 × 3 boxes
Fill the 9 × 9 grid with the digits 1 to 9. Each digit must appear exactly once in every row, every column and every 3 × 3 box. The starting clues are fixed. A number that fits the row can still be wrong if it conflicts with a column or a box.
Choose one of three difficulties
Select a difficulty before starting. Begin with the gentlest option to get comfortable with the clues, then try the more demanding grids when you want a stronger deduction challenge.
Enter numbers and pencil notes
Select a cell, then use the on-screen numbers or the 1 to 9 keys. Notes let you keep track of possible candidates. On desktop, use the arrow keys to move and N to toggle notes.
Complete a grid and continue
Finish the grid to move on to another one in the expedition. You can also finish the expedition and keep the result you have earned.
Sudoku solving tips without guessing
Start with the fullest units
A row, column or box with only a few empty cells gives you fewer candidates to compare. List the missing digits, then eliminate those already present in each crossing unit.
Look for the only possible place
Sometimes a cell has only one candidate. Sometimes a digit can go in only one cell of a row, column or box. Check both patterns before trying more complex deductions.
Update notes after each discovery
When you place a digit, review the candidates in its row, column and box. Notes are a working aid, not confirmed answers. A short, accurate candidate list is more useful than filling every cell with possibilities.
Build your score with accurate solving
A correct number earns 100 points. Each correct number adds ×0.25, up to ×5; each completed row, column or box adds another step. Completing several at once earns 150 × their count². A grid without reveals earns 1,000 points, plus 500 without mistakes. These gains use the combo and difficulty (×1 / ×1.5 / ×2). A mistake costs 100 points and ×0.5 combo. Revealing costs 250, resets the combo and removes bonuses for assisted units and this grid. Keep completing grids to increase your total. Ten mistakes across all grids end the expedition. Each difficulty has its own leaderboard.
Ten mistakes across all grids end the expedition. Each difficulty has its own leaderboard.
Back to the gameYour questions about The Sudoku
Can I play sudoku for free without installing anything?
Yes. The Sudoku runs in your browser on desktop and mobile. You can start as a guest; an eligible account is needed to attach a result to your profile and choose to publish it.
Do I need to be good at maths to play sudoku?
No. The digits identify nine different values; you do not add or multiply them. Solving means finding which value is missing and where the row, column and box rules allow it.
How many mistakes end an expedition?
Ten mistakes across all grids end the expedition. Each difficulty has its own leaderboard.
What is the difference between notes and revealing a cell?
Notes are candidates you write yourself while solving. Revealing fills a cell with its answer and applies a points penalty. Use notes for deduction, and a reveal when you decide you need help to move forward.
How do I get better at harder sudoku grids?
Work through rows, columns and boxes systematically. Start with singles, then look for digits restricted to one place. When stuck, revisit your notes before guessing or revealing a cell.