How to play sudoku
You only need one rule and a little patience. No math is involved: the numbers could just as well be symbols.
The rule
The board has 9 rows, 9 columns and 9 boxes of 3×3 cells. Fill every empty cell so each row, column and box contains the numbers 1 to 9 exactly once. The starting numbers stay put. Every puzzle here has one solution, and you can always reach it by logic.
Your first move, step by step
Pick a number and a group. Below is a real board, part of the way through, with the numbers still open pencilled into each empty cell.
76825368491549127638136846894868975232872851946682681794528349536281282872146846848568387995326872682814687468246891483282685Look at the highlighted group. Scan for where a 1 could go. Other 1s on the board rule out every cell in the group but one.
76825368491549127638136846894868975232872851946682681794528349536281282872146846848568387995326872682814687468246891483282685So the 1 goes in row 9, column 5. Placing it removes that number from the cells around it, which often opens up the next move.
768253684915491276381368468948689752328728519466826817945283495362812828721468468485683879953268726828146874682468913282685
Use pencil marks
On anything above easy, you'll want to note the numbers a cell could be. Turn on Pencil and tap numbers to add or remove them. When you place a correct number, matching notes in the same row, column and box clear themselves.
When you get stuck
- Go through the numbers 1 to 9 one at a time and scan the whole board for each.
- Check that your pencil marks are complete. Most missed moves are hiding behind a missing note.
- Learn the next pattern from the technique guides.
- Use a hint. You get three per puzzle, and undo is always free.
Keyboard controls
Arrow keys move around the board. Keys 1 to 9 enter a number, Backspace erases, P toggles pencil mode, and U undoes your last move.