Grand Theft Auto V is an action-adventure game played from either a first-person or third-person view. Players complete missions—linear scenarios with set objectives—to progress through the story.Outside of missions, players can freely roam the open world. Composed of the San Andreas open countryside area and the fictional city of Los Santos, the world of Grand Theft Auto V is much larger in area than earlier entries in the series. The world may be fully explored from the beginning of the game without restrictions, although story progress unlocks more gameplay content. Players use melee attacks, firearms and explosives to fight enemies, and may run, jump, swim or use vehicles to navigate the world. To accommodate the map's size, the game introduces vehicle types absent in its predecessor Grand Theft Auto IV, such as fixed-wing aircraft. In combat, auto-aim and a cover system can be used as assistance against enemies. Should players take damage, their health meter will gradually regenerate to its halfway point.[g] Players respawn at hospitals when their health depletes. If players commit crimes while playing, law enforcement agencies may respond as indicated by a "wanted" meter in the head-up display (HUD). On the meter, the displayed stars indicate the current wanted level (for example, at the maximum five-star level, efforts by law enforcement to incapacitate players become very aggressive). Law enforcement officers will search for players who leave the wanted vicinity. Players arrested or killed by officers during missions may restart from the last checkpoint. The meter enters a cooldown mode and eventually recedes when players are hidden from the officers' line of sight (as displayed on the mini-map).