Killer Sudoku

Killer Sudoku combines classic Sudoku with elements of Kakuro. In addition to the rows, columns and regions, within the grid are 'cages', smaller sub-regions with a number in the top left. The number is the sum of all the digits in the cage. Within a cage the numbers cannot repeat, they must all be different.

You can see why Killer Sudoku is considered one of the hardest variants. There are no given numbers and the only clues are the numbers that indicate the sum of digits in a cage. It's not all bad! In easier levels you may find one or more cages of only one cell in size. These are effectively given numbers since the clue is the sum of the cage digits and there is only one of them, so the clue is the number in the cell. If you need more help with other Killer Sudoku specific solving techniques click the link on the right.