the gameplay of "diamond" and "pearl" are much the same as previous pokémon games. the player starts the game with one pokémon, and catches more pokémon using poké balls. the player can also use his/her pokémon to battle other pokémon. when the player spots a pokémon or a trainer, the battle screen appears. during battle, the player may fight, use an item, switch pokémon, or run away from battle (the last option is not available when facing trainers). all pokémon have hit points (hp). if a pokémon's hp is down to zero, it faints and cannot battle until the player revives it. if the player's pokémon defeats the opponent's pokémon, it gets experience points. after building up enough experience points, it will gain a new level. most pokémon evolve into a new form with a new name when they reach a certain level.