Will Shortz, New York Times Crossword Puzzle Editor.
Rules For Playing KenKen®
The numbers you use in a KenKen puzzle depends on the size of the puzzle grid you choose. A 4 x 4 grid (4 squares across, 4 squares down) means you use the numbers 1, 2, 3 and 4. In a 6 x 6 grid, use the numbers 1 to 6. An 8x8 grid requires you use the numbers 1 to 8, and so on.
The numbers in each heavily outlined set of squares, called cages, must combine (in any order) to produce the target number located in the top corner of that cage using the mathematic operation indicated (+, -, ×, ÷).
The goal is to fill in all the squares so that each number is used in each row and column and no numbers are repeated in any row or column.
Here's how you play:
Do not repeat a number in any row or column.
Cages with just one square should be filled in with the target number in the top corner.
A number can be repeated within a cage as long as it is not in the same row or column.