CageDokuAnti-Knight (Chess) Sudoku Rules
By Andrew Boyko, developer of CageDoku · Updated
Anti-Knight Sudoku, also called Chess Sudoku, adds a chess rule to classic Sudoku: two cells a knight’s move apart cannot contain the same digit.
The rules
- Every row, column and 3×3 box contains 1 to 9 once.
- No two cells a knight’s move apart (two squares in one direction and one square sideways) hold the same digit.
How the rule limits peers
Every cell now “sees” its row, column, box and up to eight extra cells a knight’s move away. A newly placed digit removes candidates from all of them, so you get more eliminations from each placement.
Easy first techniques
- Knight eliminations: after placing a digit, cross it out of the knight’s-move cells.
- Hidden singles with knights: a digit’s only legal cell in a box may appear after knight eliminations remove the others.
- Combine with boxes and lines: locked candidates still apply, now with more peers.
Practice
CageDoku’s Chess variant highlights knight’s-move cells in its hints. Try one in your browser.
Frequently asked questions
Is the rule only about knight’s moves?
Yes. Kings and other chess pieces are not restricted, only knights.
Practice it in CageDoku
Free, ad-free Killer Sudoku and seven more variants. Hints name the technique and highlight the cells, so you learn why a digit goes where it goes.