Killer Sudoku
Killer Sudoku: how cages change the game
Killer Sudoku starts with an empty board. Cages replace given digits, and arithmetic becomes part of the logic.
In killer sudoku, the board starts blank. Dotted-line cages group cells together and each cage has a target sum. No digit can repeat inside a cage. You still follow standard Sudoku rules on top of that.
What makes killer different
- The board has no given digits. Every cell is empty at the start.
- Cages group adjacent cells and show a target sum in the corner.
- No digit can appear twice inside the same cage.
- Standard Sudoku rules still apply: no repeats in any row, column, or 3x3 box.
How to read a killer board
Each cage is a cluster of adjacent cells outlined by a dashed border. The small number in the top-left corner of each cage is the target sum. The digits you place inside the cage must add up to that number, with no repeats.
Single-cell cages on easier difficulties are free answers. If a cage has one cell and a sum of 7, that cell is 7. On harder difficulties those freebies disappear.
Start with the smallest cages
Two-cell cages with low or high sums have very few possible combinations. A two-cell cage summing to 3 can only be 1+2. A two-cell cage summing to 17 can only be 8+9. Those placements are your first footholds.
Once you fill a few small cages, the connected rows, columns, and boxes start narrowing down the rest. From there the puzzle plays more like regular Sudoku with extra constraints.
Use arithmetic to eliminate candidates
If a three-cell cage sums to 6, the only option is 1+2+3 in some order. The cage tells you exactly which digits belong there, just not where.
When a cage spans two boxes or two rows, you get double the elimination power. The cage constraint and the Sudoku constraint work together to pin digits down faster than either would alone.
Harder difficulties remove safety nets
Killer Easy gives you five single-cell cages (free digits) and allows five mistakes. Killer Very Hard gives you none of either. The cages also grow larger, which means more possible combinations and more ambiguity to work through.
If you can solve a medium killer without mistakes, the techniques carry straight into hard and very hard. The logic is the same; the margin for error is what changes.
Killer Sudoku questions
Can a digit repeat in a cage if the cells are in different rows?
No. A cage never allows the same digit twice, regardless of which rows, columns, or boxes the cells belong to.
Do standard Sudoku rules still apply?
Yes. Each row, column, and 3x3 box must still contain the digits 1 through 9 exactly once. Cage rules are an additional constraint on top of normal Sudoku.
What is the best first move on a killer board?
Look for two-cell cages with extreme sums (very low like 3 or 4, or very high like 16 or 17). Those have the fewest possible digit combinations.
How do I unlock Killer mode in the app?
Win a game in Redacted mode. The unlock chain is Very Hard, then Zen, then Redacted, then Killer.