Kingdom Hearts Chain of Memories

Chain of Memories is the only Kingdom Hearts game released for the Gameboy. It was released on the PlayStation 2 as Kingdom Hearts: Re: Chain of Memories in 2007.

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 says some confusing things. The path then becomes one and it leads them to Castle Oblivion. They go through each floor, experiencing their memories,among the castle floors. They start to lose their memories. A witch named Namine 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 Namine's freedom.

Meanwhile, Riku awakes down in the castle, and as he goes up the basement levels of Castle Oblivion, he must deal with the inner darkness inside of him, dealing with Xehanort's Heartless, the Riku Replica, and three members of the Organization who are trying to get Riku on their side.

Gameplay
Kingdom Hearts: CoM follows a totally new battle system as well as gameplay. The battle system now revolves around 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.

CardBreak
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 another card played afterwards.

Worlds

 * Castle Oblivion: Bosses: Axel, Larxene, Marluxia, Riku, Lexaeus, Xehanort, 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: Bosses: 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

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. Certain enemy cards are only available to Riku, and then unlocked for Sora after completing the game with Riku. Instead of leveling up HP, CP or sleights, when Riku levels up, he can increase HP, AP (Attack Power) and DP (Dark Points). After Xehanort's heartless (who is still alive) tempts he 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. In Dark Mode, Riku can use 3 powerful sleights exclusive to being in 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. Bosses exclusive to Riku's story are: Zexion, Lexaeus, and Xehanort's heartless.