Toon-Doku is a twist on classic Sudoku featuring nine selectable characters and over 200 images. Originally a pen-and-pencil game from Japan, Sudoku traveled west and started a brainteaser craze. Played on a 9x9 grid, the object is to fill the squares so that each row and column contains the numerals one through nine with none repeated. Toon-Doku adds several picture-based puzzles and a variety of single- and multiplayer modes to the basic gameplay.

Alone, players may work their way through four modes of play: "Stage," "Instant Play," "Vs. CPU," and "Edit." Single-gamers begin with only 18 available images and must unlock the rest by completing each single-player challenge. For competitive action gamers may challenge up to 16 friends through download play or take on a single opponent in such events as "Speed Battle," "Adversary," and "Single Puzzle Race." Creative gamers may create their own puzzles and share them with friends through the Piece Trade feature.