As with prior games in the series card passwords printed on TCG cards can be entered in order to obtain cards in the game. You can now get as many copies of each card as you want in this way (limited to one in previous games, except WCT 2005), but you must pay a fixed cost for each card (costs range from a few hundred DP to in excess of 10000 DP for Limited and Forbidden cards such as "Pot of Greed" and "Black Luster Soldier - Envoy of the Beginning").
Also note that although link Duels are still possible, trading cards between games is not.
Also different from the previous videogames, this one does not pit you against characters from the anime and manga (and their known Decks). Instead, you Duel against the various 'monsters' and Decks built around them (Kuriboh, Dark Magician, Cyber Dragon, etc.). The monster Duelists are organized into five different tiers, with each tier getting unlocked as the game progresses. There is also a special tier where you can Duel yourself (the opponent uses your currently selected Deck), and Copycat (who uses a Deck of your choice from one of up to 60 of your saved Deck builds).
Besides the free Dueling, there are also Challenges. These consist of Duel Puzzles (winning a Duel given certain cards on the board and in hand), Themed Duels (full Duels based on a certain theme for building your Deck), and Survival Duels (see how many Duels you can win in a row with your Life Points carrying over from Duel to Duel). As you complete certain percentages of challenges, more packs and Free Duel Duelists are unlocked.