A LITTLE FOCUS. A FRESH START.
Play Anti-Knight Sudoku
Play Anti-Knight Sudoku free online. Equal digits cannot be a chess knight’s move apart, adding a spatial twist to classic Sudoku.
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LEARN THE TWIST
How to play Anti-Knight Sudoku
You do not need to know chess strategy. Only the L-shaped move matters, and it restricts equal digits. The ordinary Sudoku rules still apply.
The rules
Fill each row, column, and 3×3 box with 1–9, without repeats. Equal digits cannot be a chess knight’s move apart: two cells in one direction and one sideways.
A useful first move
After placing a digit, inspect all of its in-bounds knight-move destinations. Some fall outside its row, column, and box, creating deductions Classic Sudoku cannot provide.
A 5 in row 4, column 4 rules out 5 at row 2, column 3 and row 2, column 5, among other knight-move destinations. Count two cells one way and one cell sideways.
SOLVE IT STEP BY STEP
Count the L-shaped move precisely
Anti-Knight gives each placed digit a set of extra exclusion cells. A knight jumps two rows and one column, or two columns and one row. It does not matter what lies between the cells. Only equal digits are forbidden at the landing positions.
- Knight-move target
- 7
Measure the displacement.
From row 4, column 4 to row 2, column 3, the row changes by two and the column by one. That is a knight’s move.
Remove the matching digit.
The target cannot also be 5. This is a new restriction here because these two cells do not share an ordinary row, column, or box.
Continue with the survivor.
Only 7 remains at the target. After placing it, inspect its own knight-move destinations. Near the edge, some of the eight possible destinations fall outside the grid and are simply ignored.
Use one digit to inspect several candidates
A digit near the middle can have eight knight-move destinations. Check all of them after a placement, especially those across box boundaries. Some destinations already share its box, so the extra rule may repeat an ordinary elimination; others provide the useful new information.
Common mistakes to avoid
- A jump of two rows and two columns is not a knight’s move.
- The rule forbids equal digits at the endpoints. It does not constrain the intermediate cells along a drawn L.
Try the reasoning yourself
From row 4, column 4, is row 5, column 6 a knight-move destination? What about row 6, column 6?
Show the answer and why
Row 5, column 6 is a destination: the differences are one row and two columns. Row 6, column 6 is not: its differences are two and two.
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
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A familiar grid, a different kind of logic. Every mode is free to play in your browser.