Killer Sudoku combines standard Sudoku rules with "cages" — groups of 2–5 cells outlined with dashed lines. The small number in each cage's corner is the sum of all digits in that cage. No digit may repeat within a cage.
Standard Sudoku rules Digits 1–9 appear once in each row, column, and 3×3 box.
Cage sums The digits in each cage must add up to the clue shown.
No cage repeats A digit cannot appear more than once within a single cage.
No given digits The grid starts completely empty — cages are your only clues.