
Sudoku rules illustrated
A completed grid highlights a row, a column and a 3×3 box to show the three standard Sudoku constraints.
A complete reference chart of the nonrepeating digit pairs for two-cell Killer Sudoku cages, covering sums 3–17.
Find the cage total in the left column. The right column lists all unordered pairs of different digits from 1–9 with that total.
For example, a two-cell cage totaling 10 permits 1+9, 2+8, 3+7 or 4+6. A pair like 5+5 is excluded because digits cannot repeat inside a cage. The chart contains all 36 possible distinct-digit pairs.
Image prepared by Sudokumax. Updated .

A completed grid highlights a row, a column and a 3×3 box to show the three standard Sudoku constraints.

A candidate diagram shows the four corners of an X-Wing and the sevens it eliminates in the shared columns.

A row-level diagram shows two cells containing only 3 and 7, followed by the candidate eliminations they allow.