Basics
The gameplay of Kingdom Hearts II is similar to the action RPG and hack and slash gameplay of the first Kingdom Hearts game, though developers made an effort to address some of the complaints with the previous game. The player directly controls Sora from a third-person camera angle, though first-person perspective is available via the 
button. Most of the gameplay occurs on interconnected field maps where battles take place. The game is driven by a linear progression from one story event to the next, usually told via cutscenes, though there are numerous side-quests available that provide bonuses to characters.
Like many traditional role-playing video games, Kingdom Hearts II features an experience point system which determines character development. As enemies are defeated, the player and allies culminate experience to "level up", in which the playable characters grow stronger and gain access to new abilities.
Combat in Kingdom Hearts II is in real-time and involves heavy hack and slash elements with button presses which initiate attacks by the on-screen character. A role-playing game menu on the screen's bottom left, similar to those found in Final Fantasy games, provides other combat options such as using magic or items, summoning beings to assist in battle, or executing combination attacks with other party members. A new feature is the "Reaction Command", special enemy-specific attacks that are triggered when the player presses the 
button at the correct time during battle. Reaction Commands can be used to defeat regular enemies or avoid damage, and are sometimes necessary to complete a boss battle. In addition to the main character, two party members are usually present who also participate in combat. Although these characters are computer-controlled, the player is allowed to customize their behavior to a certain extent through the menu screen, such as attacking the same enemy Sora targets.
Drive Gauge
One of the new features is a meter known as the "Drive Gauge". The Drive Gauge has dual functions: to transform Sora into a "Drive Form" or to summon a special character. While in a Drive Form, Sora bonds with party members to become more powerful and acquire different attributes; all but two Forms also allow the use of two Keyblades. When a Drive is executed, Sora's combat statistics are heightened. Drive Forms also give Sora new abilities that can be used in normal form, called "Growth Abilities." Sora's first two Drive Forms only combine power with one party member; later-obtained Drive Forms require him to bond with both party members. When allies are used in a Drive, they are temporarily removed from battle for its duration. Unlike the HP and MP gauges, the Drive Gauge is not refilled at save points.
Like in the first game, Sora can summon a Disney character to aid him in battle. Summons will replace the two computer-controlled characters and fight alongside Sora for as long as the Drive Gauge allows, or until Sora's HP runs out. Instead of being limited to only one action, Summons now have a menu of their own and are capable of performing solo or cooperative actions with Sora. These actions are performed by pressing the button. The Summon ability and each Drive Form are leveled up separately and by different criteria; obtaining higher levels allows for extended use and in the case of Drive Forms, access to new abilities.