Kingdom Hearts Chain of Memories

Kingdom Hearts: Chain of Memories is a Gameboy Advance sequel to Kingdom Hearts. It was published by Square Enix and developed by Jupiter, and was released in 2004. It is the second game of the series & the third game of the timeline after  Birth by Sleep &  Kingdom Hearts

Story
Sora, Donald and Goofy walk down a long path that seemingly goes nowhere. They see Pluto and start to follow him. He leads them to two paths. While deciding which path to take, a mysterious man in a black cloak approaches Sora and speaks to Sora, but at that moment his words are incomprehensible. The path then becomes one and it leads them to Castle Oblivion. The cloaked man appears as they enter the castle and gives them a card. They use the card to proceed through the castle. The first world they go to is Traverse Town, where they discover that Leon, Aerith, Yuffie, and Cid have forgotten all about them, yet they strangely remember Sora's, Donald's, and Goofy's names, where Yuffie comments, "You're not in my memory, but my heart remembers you." After Leon gives Sora a tutorial on fighting, they leave Traverse Town. The man appears once more after they arrive on the next floor. Another cloaked man appears and introduces himself as Axel. Sora battles him and when defeated, Axel gives you more cards, disappearing soon after. Sora, Donald, and Goofy go through each floor, experiencing their memories, among the castle floors. They start to lose their memories. A Nobody named Naminé begins to replace memories of Kairi with fake ones of herself. It turns out she is good and is manipulating his memories under the orders of the head of the castle, Marluxia. This escalates to a final battle in the end, for Sora's life, and Naminé's freedom.

Meanwhile, Riku awakens down in the castle, and as he goes up the basement levels of Castle Oblivion, he must take control of the inner darkness inside of him, dealing with Xehanort's Heartless, the Riku Replica, and three members of Organization XIII, Vexen, Lexaeus, and Zexion, along the way.

Gameplay
Kingdom Hearts: Chain of Memories follows a totally new battle system as well as gameplay. The battle system now revolves around Sora's memories, represented as cards. Using these cards is the only way to attack. Map Cards are used to create rooms on each floor of the castle. What appears in each room depends on what card used to get in. To obtain a map card you must defeat Heartless. Some map cards can only be obtained after getting further into the story for each of the different worlds.

Standard Uses
Each card has a number from 0 to 9. When a card is played against the enemy's card, the card with the lower value "Breaks" and is discarded. This leaves enemies vulnerable for a few seconds. Cards with a value of 0 can break any attack, but can also be broken by any card played afterwards. If a 0 is played before another high level card it will not be broken and will leave your opponent wide open for attacks.

Sleight
Main article: Sleight

Special Cards
Two types of Cards that are different from the other cards in battle are the Enemy Cards which are based off of enemies or bosses can temporarily give Sora or Riku better offensive or defensive capabilities and the Friend Cards which appear in the battlefield at certain times for pickup that can summon an ally to help fight and if enough of these cards are picked up then they can be used in a sleight.

Combining Cards
Cards can be combined into a set of three that not only creates a higher value combo that is more difficult to break, combining certain cards can activate a slight which is a special attack. The cost of combining cards is that the first card used in the combo cannot be reloaded when the deck is reloaded, although certain items such as Elixir and Mega-Elixir can reload any unreloadable cards.

Sora's Gameplay
Sora can use any available card to create up to three decks as long as they don't exceed his Card Point (CP) limit and have at least one weapon card in his deck. During Level Up's Sora can increase his Card Points, in addition to obtaining more HP and new slights at certain times. Other than using Weapon, Magic/Summon, and Items cards Sora can also use Premium cards which are special cards for the weapon and magic. These cards do not require as much CP to equip although they can become unreloadable cards when used, with the minor exception as the second or third card in a combo. Other than using Moogle shops to obtain additional cards such as weapon cards that have higher attributes. There are certain cases where Sora has to earn the card through the storyline first before it become available in a Moogle Shop.

Worlds

 * Castle Oblivion: Bosses: Axel, Larxene, Marluxia, Riku, Lexaeus, Xehanort's Heartless, Vexen.
 * Traverse Town: Boss: Guard Armor.
 * Wonderland: Bosses: Card Soldiers, Trickmaster.
 * Olympus Coliseum: Bosses: Cloud Strife, Hades.
 * Agrabah: Boss: Jafar
 * Hollow Bastion: Boss: Maleficent
 * Halloween Town: Boss: Oogie Boogie
 * Monstro: Boss: Parasite Cage
 * Destiny Islands: Bosses: Darkside, Zexion (Re:Chain of Memories only)
 * Neverland: Boss: Captain Hook
 * Atlantica: Boss: Ursula
 * Twilight Town: Bosses: Vexen, Riku Replica

Deep Jungle didn't appear in this game as in the first Kingdom Hearts Sora crash lands the ship and lands in the treehouse and it was an accidental memory so it never appeared in Castle Oblivion.

Reverse/Rebirth Mode
After completing the game as Sora, a new challenge arises. Reverse/Rebirth mode follows Riku as he climbs the basements of Castle Oblivion. Riku's deck cannot be changed, however, it changes automatically as time goes on. Riku does not not need as much time to reload his deck. Certain enemy cards are only available to Riku, and then unlocked for Sora after completing the game with Riku. Riku can only keep the enemy cards that are based off of the bosses after winning them during battle, the others are available in one world only.

Instead of leveling up HP, CP or sleights, when Riku levels up, he can increase HP, AP (Attack Power), or DP (Dark Points). After Xehanort's Heartless (who is still alive) tempts the darkness in Riku's heart Riku can use his dark powers during battle. These powers are triggered by taking damage or breaking his opponent's cards, when the Dark Points exceed 30 or above, Riku will automatically go into Dark Mode. In Dark Mode, Riku can use 3 powerful sleights exclusive to his Dark Mode: Dark Aura, Dark Firaga, and Dark Break (These attacks were used by the Riku Replica in Sora's story.) How long Dark Mode lasts depends on how much DP he has.

Riku does not have access to any of the friend cards that Sora had. Instead, he has King Mickey as his friend card. Using Mickey heals Riku, reloads the deck, and stuns enemies for a few seconds. Using more Mickey cards at once increases the power of this attack. Because of his inability of using magic cards Riku cannot heal as easily during battle limiting it to the Oogie Boogie and Search Ghost Enemy cards in addition to Mickey Mouse. Bosses exclusive to Riku's story are: Zexion, Lexaeus, and Xehanort's Heartless.

Remake
Kingdom Hearts: re-Chain of Memories was a Playstation 2 remake released in a package along with Kingdom Hearts II: Final Mix+. The game featured 3-D graphics and voice-acting, along with all-new cards and cutscenes. Square Enix announced that it will be released in the US on the 2nd of December, 2008.