The rules of calcudoku
Calcudoku is the arithmetic logic puzzle made famous by KenKen. Fill an N×N grid — here 4×4, 5×5 or 6×6 — so every row and every column contains the numbers 1 through N exactly once. The grid is divided into cages; the numbers in each cage must produce the cage's target number with its operator. Every puzzle has exactly one solution.
The six rules
- Fill every blank cell with a number from 1 to N, where N is the grid size.
- Every row must contain each number 1 to N exactly once.
- Every column must contain each number 1 to N exactly once.
- Each cage's numbers must reach its target: + sums them, × multiplies them, − takes the difference of a two-cell cage, and ÷ takes the exact quotient of a two-cell cage.
- Digits may repeat inside a cage — only rows and columns forbid repeats.
- There is exactly one solution, reachable by logic.
How to read the grid
The thick lines mark the cages. Each cage shows its target number and operator in the corner — "12+" means the cage's numbers must add to 12, "6×" means they must multiply to 6. A cage with just a lone number is a one-cell cage: the number is simply given, like a sudoku clue.
The cage operators
For a two-cell cage, − means the difference of the two numbers and ÷ means their exact quotient (the larger divided by the smaller — here it always comes out even). For any cage, + means the sum of all its numbers and × means their product. A cage can hold two, three, four or more cells, and the operator works across all of them.
One more thing: repeats inside a cage
This is what separates calcudoku from killer sudoku. In killer sudoku every cage is a set of distinct digits; in calcudoku the digits inside a cage may repeat, as long as no row or column repeats them. So a 2-cell "4+" cage in a 4×4 puzzle could hold 2 and 2 — a pair that would be illegal in killer sudoku.