Hard Sudoku
Hard Sudoku from our Tough band: as few as 24 starting numbers and long stretches where the only way forward is a chain of locked candidates. Every grid is still pure logic. If you get stuck, Hint names the rule that proves the next move, so you learn the pattern rather than just the answer.
- Tap a square, then tap a number to place it. Tap the same number again to take it back.
- Every row, every column and every 3x3 box holds the digits 1 to 9 exactly once.
- Switch on Notes to pencil in the candidates for a square. On the harder levels you will need them.
- Finished? Tap Play again for a fresh grid at the same difficulty.
🎯 Objective
Fill all 81 squares so the digits 1 to 9 appear exactly once in every row, every column and every 3x3 box. Every grid has one solution that logic alone can reach.
📊 How you score
Practice grids score points the same way the daily does, higher for harder grids and lower for time, hints and slips, so you can see how a solve went. They are not saved to the leaderboard or your solve streak: only the daily grid counts for those, and you can play as many practice grids as you like.
💡 Tips
- Scan for the digit that is already placed most often. The more copies on the board, the fewer squares are left for the next one.
- Work a box, a row and a column that all cross the same empty square. A digit ruled out by any one of them is ruled out for good.
- From Thursday on, pencil marks stop being optional. A square with only two candidates is the thread to pull.
- Two squares in a unit holding the same two candidates lock those digits away from every other square in that unit.
- Stuck? Tap Hint below the board. Three hints per grid, and each one names the rule that proves the move, then shows you the square and its digit, so you learn the pattern rather than just the answer.
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