In sudoku, you have to place the numbers 1 to 9 into a square 9-by-9 grid. There are nine 3-by-3 blocks within that grid and you have to place the numbers in each block, row and column so there are no ...

Killer sudoku is similar to the other levels in that each of the numbers 1-9 must fit into each 9-by-9 square. No number can ...