Battles are carried out using a CCG-styled system. Whereas most CCGs use a turn-based system, Kingdom Hearts: Re: Chain of Memories
folds card attacks into the action-based system used in the two console games. At the start of each battle, Sora is dealt a hand of cards which can be cycled by pressing the shoulder buttons. Each card relates to battle actions such as a Keyblade (attack), spell, item, or summon. Cards can be played as single actions or in combination, which unlock combos or special attacks (called Sleights). Casting spells in combination will result in more powerful spells (Firaga, Blizzaga...).
Each card also has a number on it, ranging from 0 to 9. These numbers indicate how strong the card is in relation to the cards that your opponent can play. Higher numbers beat lower numbers, with "0" acting as a wild card that beats anything. Numbers also determine which Sleights are used in battle.
Similar to the card-based dungeon exploration, the combat system is an interesting concept, especially in how it manages to combine systems that are, at a gameplay level, completely different. Yet, as already mentioned, it doesn't come together as well as it could. With a good hand, you can easily blast through a simple battle, but when it comes to thinking strategically (a key trait in any CCG), the pacing doesn't cooperate. Blowing through cards in combat also leads to numerous shuffles, adding another hitch to the pacing. Deciding to play a more strategic hand also works, but requires near mastery of the system and a lot of luck.
Back in 2004, I said that despite its problems, Chain of Memories was still worth playing through, but now I'm not so sure. With time, most of the allure has been lost; nearly all of the game's mysteries have been unlocked, adding little incentive for a play through. Even for the most die-hard of Kingdom Hearts fans, Kingdom Hearts Re: Chain of Memories probably isn't worth your time unless you really need more time with Sora or just like complicated game mechanics.