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How to play X-Sudoku (Diagonal Sudoku)

X-Sudoku, also called diagonal Sudoku, is a Sudoku variant where the two main diagonals must each contain the digits 1 through 9 with no repeats — on top of the usual row, column and 3×3 box rules. The extra constraint gives you more ways to deduce each digit.

1. 1Fill rows, columns and boxes. Every row, every column and each of the nine 3×3 boxes must contain the digits 1–9 with no repeats — exactly like classic Sudoku.
2. 2Solve the diagonals too. The two highlighted long diagonals must also each contain 1–9 with no repeats. Treat them as two extra regions.
3. 3Scan for forced digits. Look for cells where only one digit can legally go, using the row, column, box and diagonal a cell belongs to.
4. 4Use Notes for candidates. Tap Notes to pencil in the possible digits for a cell, then eliminate them as you place numbers elsewhere.
5. 5Finish for a speed bonus. Complete the grid as fast as you can — your solve time becomes points with a speed bonus, and daily solves build a streak.

Tips & strategy

Start on the diagonals: because they add a constraint most Sudoku solvers ignore, a digit that looks ambiguous in its box is often forced once you check the diagonal it sits on. Whenever a normal Sudoku scan stalls, re-scan the two diagonals for the next breakthrough.