Most SuDoku puzzles may be easier than others to solve, but there's a variation of SuDoku that is perhaps harder than all the rest. This is Killer SuDoku. The name says it all. The rules are exactly the same as the original SuDoku, but with an additional rule - numbers in the dotted line area must add up to the number at the top left of that area. Good luck in solving it - you'll need it!
