The Kingdom Hearts series games contain elements from both action and role-playing games. The games are driven by a linear progression from one story event to the next, usually shown in the form of a cut scene, though there are numerous side quests available that provide bonus benefits to the characters. The player primarily controls the principal protagonist of the series, Sora. Sora is usually accompanied by Donald Duck and Goofy, who are non-playable characters that aid Sora in battle. While visiting certain worlds, Donald or Goofy can be swapped out for that world's protagonist (e.g. Jack Skellington while visiting Halloween Town or Aladdin while visiting Agrabah) In the first and third game, their behavior can be altered to suit different combat objectives. The games feature real-time combat that incorporates physical attacks, magic, and summonings, though each game handles battles differently.