Sudoku

Play Sudoku, filling a 9 × 9 grid with the numbers 1 to 9, at four levels: Easy, Medium, Hard and Expert. Every puzzle is newly generated and checked to have exactly one solution.

How to use

1. Choose the "Difficulty" and press "New puzzle", or press "Today's puzzle" to play the same grid as everyone else today.
2. Tap a cell or move with the arrow keys, then enter 1 to 9 with the on-screen pad or the keyboard.
3. Switch on "Notes" to write candidate numbers. Use "Erase" or "Undo" to fix mistakes.
4. If you are stuck, "Hint" reveals one cell and "Check answers" shows how many cells are wrong so far.

How it works

• Rule: every row, every column and every 3 × 3 box outlined in bold must contain each number from 1 to 9 exactly once.
• Easy and Medium puzzles are made to be solvable by finding cells where only one number fits. Hard and Expert puzzles are made to need harder techniques, such as candidate pairs.
• "Today's puzzle" is the same for everyone on the same date and level. "Print" prints the empty puzzle.
• Progress is saved on this device automatically. Pausing stops the timer and hides the grid.

Questions and answers

What are the rules of Sudoku?

Fill the empty cells with 1 to 9 so that no number repeats in any row, column or 3 × 3 box. The numbers given at the start cannot be changed.

How do you solve Sudoku?

Start with cells where only one number fits, or with a row, column or box where a number has only one possible place. When that runs out, write candidates with "Notes" and narrow them down.

How is the difficulty decided?

By the number of given numbers and the techniques needed to solve the puzzle. Easy puzzles have about 38 givens; harder levels have fewer givens and need harder techniques.

Does it show repeated numbers?

With "Mark repeated numbers in a row, column or box" on, repeated numbers are marked. A number that does not repeat but is still wrong is found only with "Check answers".