Stealth has become a common concept in video games today. However, there are a few games that rely on it as the core of their gameplay. The Metal Gear, Tenchu, Thief and Splinter Cell franchises all feature stealth as a main gameplay aspect.
Stealth has made its way into almost every First Person Shooter since the debut of GoldeneEye on the Nintendo 64 and especially Metal Gear Solid on the PlayStation. Recent titles to apply the stealth concept to the FPS genre include Crysis and S.T.A.L.K.E.R.: Shadow of Chernobyl.
The ultimate example of a game that uses stealth as its core concept and basis for gameplay is the Metal Gear series of games. It is believed that the stealth concept came into being because of the technical limitations of the 8-bit MSX and NES platforms. No more than three enemies could be rendered on the screen at the same time, so creator Hideo Kojima had to implement a different style of gameplay, resulting in the revolutionary stealth-based gameplay of the original Metal Gear.
In Metal Gear 2: Solid Snake for the MSX2 and its popular sequel Metal Gear Solid for the Playstation, each guard has a field of view in which they can spot the player or investigate the area. This field of view is visible to the player via their in game heads up display, as a part of their radar. A core component of gameplay is to avoid these fields of view, and maintain stealth while still accomplishing an objective. To maintain stealth, the player can utilize the environment by crawling through airducts or under cars, or simply hiding around corners. They can also use their equipment. Using a silenced firearm to kill guards, or using a chaff grenade to disable a security camera are common methods of maintaining stealth. Disabling guards by knocking them out or killing them will alert other guards if the body is discovered. In this situation, maintaining stealth includes hiding or disposing of the body, such as stuffing it into an available locker or if on a ship, dumping it overboard.
While Metal Gear Solid has stealth elements, there are action combat sequences. If the player is detected, guards enter an alerted status, and the player will be forced to fight an overwhelming number of guards. During the alert sequence, the player can use weapons and other equipment to kill or disable reinforcements. The game remains in the alert sequence until the player finds a way to escape their detection. All boss characters are unavoidable, and must be fought.
Metal Gear Solid 2: Sons of Liberty introduced new abilities such as leaping over and hanging off of railings, opening and hiding in storage lockers, and sneaking up behind enemies to hold them at gunpoint for items and ammunition. The environment also had a greater impact on the stealth gameplay, taking into account factors such as weather, smell, atmosphere and temperature. The game also introduced a collective enemy AI, where the enemy guards work together in squads, can communicate with one another, and react in a more realistic manner. The game also expanded its predecessor's cover mechanic, with Snake or Raiden now able to take cover behind walls or objects and pop out to shoot, while enemies could also take cover and pop out to shoot at the player or throw grenades.
Metal Gear Solid 4: Guns of the Patriots deviated from the stealth aspects more than any of the previous games in the series with much more action-oriented gameplay; many players opted to approach it more like an action game than a stealth game.
Another franchise that features the stealth concept is the Splinter Cell series. At first, the series seems very similar to the Metal Gear series of games. Where the two franchises differ is how they handle stealth. The guards in the Splinter Cell series have a wide cone of sight, so in order to remain unnoticed, players must utilize dark areas in order to maintain stealth. Gameplay features a light meter that tells players whether they are in a area of darkness suitable to maintain stealth. If the light level is low, guards cannot see the player. if light levels are high, they can spot the player from a good distance away.
Unlike the Metal Gear series, detection can mean the automatic failure of a level. Often, the best course of action in the Splinter Cell series of games is to avoid detection altogether. Player weapons are a silenced pistol and a silenced automatic rifle, but they are not effective unless used to make headshots. Combat is discouraged and the player can get overwhelmed easily by a few enemy guards. Also differing from the Metal Gear series, the player cannot take as much damage and cannot carry any healing items in inventory, they have to be found and used on the spot.
While the game does have action sequences, they are not the focus of the game. Objectives can change from mission to mission, requiring that you not be detected, or not kill, so it can be difficult at times. Later games in the series feature a sound meter. This meter indicates to the player how much sound they are making in relation to the environment, and if the sound levels are suitable to maintain stealth.