Zombie Sudoku

Play Sudoku for free. But instead of numbers, use the undead. In Sudoku, numbers are arbitrary—there's no adding, subtracting, etc. So why not flex some logographical muscles. And why not zombies. There are nine zombies: one for each number in a typical 9x9 Sudoku game. The challenge is to step away from numerical logic and exercise visual thinking. There are four levels of difficultly, hints are available, and numbers can be activated. But the only score is time, and the only competition is you.