Progression through "Paper Mario" depends upon interaction with the game's non-player characters (NPCs), who would often offer clues or detail the next event in the storyline. As in other RPGs, the player can find or purchase items from NPCs to help in and outside of combat. Badges can also be obtained that yield bonuses ranging from added moves to gradual health restoration during combat; each consumes a set number of Badge Points (BP), meaning Mario can only equip a limited number of badges at a time. Princess Peach is playable at particular points in the game as a recurring quest line. The objectives and actions of each transition to Peach vary, although most are stealth-based.