The basic mechanics of Ruby and Sapphire are largely the same as their predecessors'. As with all Pokémon games for hand-held consoles, gameplay is in third-person, overhead perspective and consists of three basic screens: a field map, in which the player navigates the main character; a battle screen; and the menu, in which the player configures his party, items, or gameplay settings. The player begins the game with one Pokémon, and can capture more using Poké Balls. The player can also use his/her Pokémon to battle other Pokémon. When the player encounters a wild Pokémon or is challenged by a trainer to a battle, the screen switches to a turn-based battle screen where the Pokémon fight. During battle, the player may fight, use an item, switch his/her active Pokémon, or flee (the last not an option in battles against trainers). All Pokémon have hit points (HP); when a Pokémon's HP is reduced to zero, it faints and cannot battle until it is revived. If the player's Pokémon defeats the opposing Pokémon (causes it to faint), it receives experience points. After accumulating enough experience points, it may level up; most Pokémon evolve into a new species of Pokémon when they reach a certain level. Apart from battling, capturing Pokémon is the most essential element of Pokémon gameplay. During battle with a wild Pokémon (other trainers' Pokémon cannot be captured), the player may use a Poké Ball on the wild Pokémon. If successful, the Pokémon will be added to the player's active party (or stored if the player already has the maximum six Pokémon in his/her party). Factors in the success rate of capture include the HP of the target Pokémon and the strength of the Poké Ball used: the lower the target's HP and the stronger the Poké Ball, the higher the success rate of capture is.