Mayhaps others here have already discovered KenKen puzzles, which are like suped-up Sudoku, but I just found them recently and now all my productivities are belong to them.
A few can be found online
here.
I've made it up to solving 7x7 puzzles, which killed my entire work day.
A tip for those starting out -- forget the traditional left to right order of operations. If the desired outcome for a cage is "3" with the mathematical operation being "-", the order could be 5,2 or 2,5. Same goes for division. (This will make more sense after you've tried one)
KenKen - Addicting Puzzle Game
