THE PLAYBOOK · QTHCC
How to play Diagonal Sudoku
This QTHCC page combines Diagonal Sudoku with a guide to the decisions it asks you to make. Fill all cells with 1–9; do not repeat a symbol in any row, column or region. The two long diagonals must also contain each symbol once. Use control confidence to give your round a clear purpose.
Control confidence
Check the controls before starting. On a touch screen, keep the game area visible and use the labelled buttons where they are provided.
Your goal
Fill all cells with 1–9; do not repeat a symbol in any row, column or region. The two long diagonals must also contain each symbol once.
Step by step
- Select an empty cell. The original clues cannot be edited.
- Choose a symbol from the number pad, or type it on a keyboard.
- Turn Notes on to record candidate symbols without committing an answer.
- Use Check entries to check your filled values. Hint reveals one value from the verified solution.
- Complete the board, or choose New puzzle for another board.
Controls
Tap or click a cell and use the number pad. Keyboard: arrows select cells; digits (and A–G on 16×16) enter values; Backspace erases.
A useful example
Before filling a cell, compare the symbols already used in its row, column and 3 × 3 region. A candidate must be absent from all three. The two long diagonals must also contain each symbol once.
Watch out for this
Notes are reminders, not final entries. A full board only counts as complete when it satisfies every rule.
Common questions
Which controls should I use?
Tap or click a cell and use the number pad. Keyboard: arrows select cells; digits (and A–G on 16×16) enter values; Backspace erases.
Can you show a concrete example?
Before filling a cell, compare the symbols already used in its row, column and 3 × 3 region. A candidate must be absent from all three. The two long diagonals must also contain each symbol once.
What is included in this edition?
A real 9 × 9 puzzle with 3 × 3 regions, candidate notes, undo and saved progress. Every included puzzle is checked for a unique solution.
