Zendoku is a variation of Sudoku, offering a slightly more combative experience than simply lining up numbers. Players must now insert symbols, rather than the standard numbers. Players choose characters and choose to attack or defend against a challenger, which takes place via mini-games started upon filling in a group of numbers. The game is set against anime-influenced backdrops and has a "light-hearted martial arts" theme. The game also offers single-player puzzles. Source: Wikipedia, "Zendoku", available under the CC-BY-SA License.