genre thus incorporate elements of driving simulation games. Some games even allow players to customize their vehicles. Players can engage in combat using a range of weapons depending on the game setting, such as firearms, explosives, close-range melee weapons, or even exaggerated fictional weapons (e.g. laser weapons or a hand-held minigun) . As such, several reviewers have stated that games in this genre are partially third-person shooters. Players can find weapons scattered throughout the game world, and may buy weapons in shops or take them from dead enemies. Virtually anyone in the game world can be attacked by the player. In many games, excessive violent behavior will provoke a reaction by police authorities, who the player may then choose to fight or evade. Players must also keep track of their health and ammunition in order to succeed in combat. These games have employed a variety of aiming mechanisms, such as free look aiming or a "lock-on" button. Several games have been criticized for difficult or burdensome controls when it comes to shooting, and thus video game designers have tried to refine the aiming and shooting controls in these games. Open world and missionsGrand Theft Auto clones allow players to freely explore the game world, which is typically on the scale of an entire city. Some games base their level design on real world cities, such as London, New York City, and Los Angeles. Players are usually able to navigate by vehicle or on foot. Some games put greater emphasis on leaping, climbing, and even swimming. Exploring the world is not just necessary to complete objectives, but also to gain valuable items, weapons, and vehicles. Different parts of the game world may be controlled by different enemy factions, who will attempt to stop the player in a variety of ways. However, more recent games in this genre allow players to acquire their own territory. The freedom of navigating a huge game world may be overwhelming or confusing for new players. Game designers have come up with a variety of navigational aids to solve this problem. A mini-map feature is common, while Saints Row and Grand Theft Auto IV go so far as to offer a GPS service. Games without these navigation tools are sometimes criticized as confusing. The player's freedom to explore may be limited until they complete certain objectives and advance the game plot. Players must visit specific locations and