Killer Sudoku is deemed to be one of the most challenging of Japanese puzzles, hence the rather unpleasant name. While it can be devilishly difficult, it is, in fact, a rather pleasing conflation of Sudoku and Kakuro.
In addition to the rules of normal Sudoku, the sum of the digits in each inner shape (or cluster) must equal the number in the top-left corner of each shape.
Our interactive version of this puzzle includes special features that will, we believe, improve your solving skills. Use of the Inspector and the Clusters Calculator is highly recommended. Take a moment to read the Help file in the puzzle window, in order to take full advantage of these features.
If you are new to Killer Sudoku, refer to the Puzzler Encyclopedia for further details.