Killer Sudoku +!

Killer Sudoku is a fun and challenging variant of Sudoku. If you love Sudoku, why not give Killer Sudoku a try?As with Sudoku, the objective of Killer Sudoku is to fill the grid with the numbers 1 to 9 such that each row, column and nonet (3x3 group of cells) contains each number only once. The puzzles are graded into difficulty levels, all excellent quality and with a unique solution.