Source: Wikipedia, "[en.wikipedia.org/wiki/Yu-Gi-Oh%21_World_Championship_Tournament_2004 Yu-Gi-Oh! World Championship Tournament 2004]", available under the CC-BY-SA License.
The player can assemble a deck and can duel against a variety of computer opponents. The game features the first 1,138 cards released in Japan. There are 29 opponents in the game, however duelist 29 can't be played and is locked when Marik is at least once defeated. Each opponent has different skills and decks revolve around a certain theme (Yugi=Basic, Exodia Rare Hunter=Exodia, Yami Yugi (Dark Yugi)=Ultimate, etc.).