A LITTLE FOCUS. A FRESH START.
Play Anti-King Sudoku
Play free Anti-King Sudoku online. Stop equal digits from touching diagonally while solving rows, columns, and boxes across five levels.
Get the iPhone app
OneStop Sudoku, wherever you go.
Website saves stay in this browser and don’t transfer to the app.
Scan to downloador tap to open
The game loads here. Choose a difficulty to start or resume a puzzle.
LEARN THE TWIST
How to play Anti-King Sudoku
Classic already prevents equal horizontal or vertical neighbors. Anti-King adds the diagonal contacts of a chess king’s move; it does not restrict all cells on a long diagonal.
The rules
Fill each row, column, and 3×3 box with 1–9, without repeats. Equal digits cannot touch diagonally, as if they were a chess king’s move apart.
A useful first move
Pay particular attention to diagonal neighbors across box boundaries. Inside a single box, its usual no-repeat rule already makes the same deduction.
A 4 at row 3, column 3 prevents 4 at row 4, column 4, even though those cells belong to different boxes. Equal digits cannot touch at a corner.
SOLVE IT STEP BY STEP
Check the corners where ordinary boxes meet
Ordinary Sudoku already prevents equal digits from being side by side. Anti-King also prevents a matching digit one cell diagonally away. The most useful extra deductions often occur at a box boundary, where diagonal neighbors do not share an ordinary box.
- Diagonal neighbor
- 6
Look one step diagonally.
The target is exactly one row down and one column right from the 4. Those cells touch at a corner.
Apply the Anti-King restriction.
Even though the cells are in different boxes, they cannot both be 4. Remove 4 from the target.
Update nearby corner contacts.
The target must be 6. Its diagonal neighbors cannot be 6, and its row, column, and box must also be updated.
Separate short contacts from long diagonals
The extra rule reaches only one cell diagonally. Two equal digits farther apart on a diagonal may be allowed if ordinary Sudoku permits them. Scan the four diagonal neighbors of a placement; do not treat the entire diagonal as another row.
Common mistakes to avoid
- Anti-King is not Diagonal Sudoku: an unmarked long diagonal does not need all nine digits.
- Inside one ordinary box, equal diagonal neighbors are already forbidden. Look across box borders for deductions that add something new.
Try the reasoning yourself
Does a 4 at row 3, column 3 rule out 4 at row 5, column 5 solely because of Anti-King?
Show the answer and why
No. The cells are two rows and two columns apart, beyond the one-step restriction. Other rules or placements could still rule out that 4, but Anti-King alone does not.
Controls, difficulty, and saved games
Choose Beginner, Easy, Medium, Hard, or Expert above. Select an empty cell, then tap a number or use your keyboard. Notes let you pencil in candidates; three hints are available. Three mistakes end the puzzle.
Every mode and difficulty keeps a separate save in this browser. You can switch puzzles and return to your place. Clearing site data removes these saves; they do not sync with another device or the iPhone app. Settings include night mode and optional automatic cell advancement.
Correct entries earn points. High scores are stored by mode and difficulty and update only when beaten; completed-puzzle count and day streak are shared.
FIFTEEN WAYS TO PLAY
Explore all Sudoku modes
A familiar grid, a different kind of logic. Every mode is free to play in your browser.