Sudoku

Expert sudoku

Expert sudoku brings in patterns that link cells in different rows, columns and boxes. A puzzle here can need an X-Wing, where one number is limited to the same two columns in two different rows, or an XY-Wing, where three cells with two candidates each force a number out of the cells that see them.

Full pencil notes are close to essential at this level. If these patterns are new to you, the Practice mode drills them one at a time.