How to play Killer Sudoku
- Fill every row, column and 3 by 3 box with the digits 1 to 9, each once, as in normal sudoku. Click a square, then a number on the pad or your keyboard.
- The dashed outlines are cages. The digits in a cage must add up to the small number in its corner, and a digit can’t repeat inside a cage.
- Pick a square and the panel lists the digit sets that could fill its cage. Turn on Notes to pencil in possibilities, and use Hint when stuck.
Strategies for Killer Sudoku
Start with the cages that have only one possible set: 3 in two squares is 1 and 2, 4 in two is 1 and 3, 16 in two is 7 and 9, 17 in two is 8 and 9, 6 in three is 1, 2 and 3, and 24 in three is 7, 8 and 9.
Then use the rule of 45. Every row, column and box adds up to 45, so add the cages that sit fully inside a box and the difference from 45 is the total of the squares left over. Cages and lines also work together: if a cage must contain a digit and the whole cage sits in one row, that digit can’t appear anywhere else in the row.
Keep your notes short. Pencil in only the digits from the cage’s possible sets (the cage helper lists them), and remove them as rows, columns and boxes fill in.
About the game
Killer Sudoku combines sudoku with the sums of kakuro. The grid is the usual 9 by 9, but instead of many given numbers it’s divided into cages, each with a total. The digits in a cage add up to that total and don’t repeat. This version makes a new puzzle each time, checks it has exactly one solution, and keeps one game per level on this device.