Expert Diagonal Sudoku
The ultimate test. Expert Diagonal Sudoku puzzles push the variant constraint to its limit, requiring flawless logic and the most advanced solving techniques. Only the sharpest minds complete these.
What to expect at Expert level
Expert Diagonal Sudoku puzzles are constructed to be as difficult as possible while remaining logically unique. Every cell placement flows from precise reasoning - Guessing never helps. The constraint creates complex cross-cell dependencies that demand full concentration.
Designed for solvers who have mastered Hard and are looking for the definitive Diagonal Sudoku experience.
Difficulty overview
About Diagonal Sudoku
In Diagonal Sudoku, the standard 9×9 rules apply — but with one powerful extra constraint: both main diagonals (top-left to bottom-right, and top-right to bottom-left) must each contain every digit from 1 to 9 exactly once. This extra constraint typically makes the puzzle easier to solve since diagonals act as two extra units for elimination.
Solving Techniques for Expert Level
| Technique | Description | Level |
|---|---|---|
| Diagonal as a Unit | Treat each diagonal exactly like a row or column — every digit 1–9 appears exactly once. Standard scanning and counting apply. | Beginner |
| Diagonal–Box Interaction | When a digit on a diagonal is confined to one box segment, eliminate it from the rest of that box. | Intermediate |
| Diagonal Naked Pairs | If two cells on a diagonal share the same two candidates, eliminate those values from all other diagonal cells. | Intermediate |
| Three-Unit Intersection | A cell on the main diagonal also belongs to a row, column, and box — four constraint units simultaneously — maximising elimination power. | Advanced |