Stealth game

Stealth game is a video game genre in which the player must avoid detection, using stealth to evade or ambush antagonists. Games in the genre employ mechanics such as hiding in shade, disguises, and noise which can alert enemies. Some games allow the player to choose between a stealthy approach or directly attacking antagonists, perhaps rewarding the player for greater levels of stealth. The genre has employed espionage and counter-terrorism themes, with such protagonists as special forces operatives, spies, and ninjas. Some games have employed stealth game elements with those of other genres, such as first-person shooters or platform games.

Some of the early games revolving around stealth include Castle Wolfenstein (1981), Metal Gear (1987), and Metal Gear 2: Solid Snake (1990). According to the New York Times, "once upon a time, stealth in games was rare. This began to change in 1998", while Maximum PC has said "Some would argue that the stealth-action genre was born in 1998" with the mainstream success of Metal Gear Solid as well as Tenchu: Stealth Assassins and Thief: The Dark Project. Tenchu: Stealth Assassins was the first 3D game in the genre, while Metal Gear Solid, released some months later, transformed the relatively obscure Metal Gear series into a highly acclaimed, profitable franchise with numerous sequels. Thief: The Dark Project pioneered 3D stealth games on PC. These influential games inspired other successful series, such as Hitman and Splinter Cell. Later games in the genre have allowed the player to choose between, or combine, stealth tactics and direct confrontation. The genre's best selling game to date is Assassin's Creed II with over 8 million in sales.

Definition
Unlike most action games, stealth games challenge the player to avoid alerting enemies altogether. The core gameplay elements of the modern stealth game are to avoid combat, minimize noise, and strike enemies from the shadows. There are usually multiple ways to achieve a goal with different pathways or styles of play. Some games offer a choice between killing or merely knocking out an enemy. Players can hide behind objects or in shadows, and can strike or run past an enemy when they are facing the other way. If the player attracts the attention of enemies, they usually must hide and wait until the enemies abandon their search. Thus, planning becomes important, as does trial-and-error. However, some stealth games put more emphasis on physical combat skill when the player is spotted.

Game design
Because the player can often hide in the dark, light and shadow become important parts of the level design. Usually the player is able to shoot and disable certain light sources. Stealth games also emphasize carefully designed audio, because players must be able to hear the subtle sound effects that may alert enemies to their actions. Noise will often vary as the player walks on different surfaces such as wood or metal. Players who move recklessly will make more noise and attract more attention.

In order for a game to include stealth gameplay, the knowledge of the artificial intelligence must be restricted to make it ignorant to parts of the game world. Artificial intelligence is carefully crafted for the stealth game experience and enemies must have logical reactions to what the player does, such as when the player turns off the lights. Enemies typically have a line of sight which the player can avoid by hiding behind objects, staying in the shadows or moving while the enemy is facing another direction. Enemies can also typically detect when the player touches them or moves within a small, fixed distance. Overall, stealth games vary in what player actions the AI will perceive and react to, with more recent games offering a wider range of enemy reactions. Often, the AI's movements are predictable and regular, allowing the player to devise a strategy to overcome his adversaries.

Although games like Thief: The Dark Project are designed entirely around stealth gameplay, other games occasionally pose challenges where victory can only be achieved by stealth. In these situations, players must avoid discovery or combat to complete a mission.

Early stealth games
Castle Wolfenstein, originally available on the Apple II in 1981, employed stealth elements as a focus of the gameplay. Players were charged with traversing the levels of Castle Wolfenstein, stealing secret plans and escaping. Players could acquire uniforms to disguise themselves and walk by guards undetected. The game spawned a sequel, Beyond Castle Wolfenstein, in 1984. It included some additions such as a dagger for close-range kills and a greater emphasis on disguising in enemy uniform. id Software's technically updated 1992 remake Wolfenstein 3D was originally going to feature some of the original's stealth gameplay, such as body hiding, but this was cut to make the game faster paced. This Wolfenstein game would ironically pave the way for quite a few later 3D action games, specifically first-person shooters.



Hideo Kojima's Metal Gear, released in 1987 for the MSX2 and the Nintendo Entertainment System in 1988, utilized stealth elements within an action-adventure framework, and was the first mainstream stealth game to be released on consoles. Since the MSX2 was not available in North America, only the NES version was released there. Metal Gear placed a greater emphasis on stealth than earlier games, with the player character Solid Snake beginning without any weapons (requiring him to avoid confrontation until weapons are found), enemies able to see from a distance (using a line-of-sight mechanic) and hear gunshots from non-silenced weapons, security cameras and sensors at various locations, and a security alarm which sounds whenever Snake is spotted and causes all enemies on screen to chase him. Snake could, however, disguise in enemy uniforms and cardboard boxes.

A sequel, Metal Gear 2: Solid Snake, was released in 1990 for the MSX2. It was the first game to coin a name for the genre, "Tactical Espionage Game", and it further evolved the stealth gameplay of its predecessor. The player had more abilities, such as crouching, crawling into hiding spots and air ducts, distracting guards by knocking on surfaces, and using a radar to plan ahead. The enemies had improved AI, including a 45-degree field of vision, turning their heads left and right to see diagonally, the detection of various different noises, being able to move from screen to screen (they were limited to a single screen in earlier games), and a three-phase security alarm (where reinforcements are called in to chase the intruder, then remain on the lookout for some time after losing sight of the intruder, and then leave the area). The game also had a complex storyline and improved graphics. It was only released for the MSX2 in Japan, however, which limited its accessibility to US gamers. Instead, an alternative Metal Gear sequel named Snake's Revenge was released for the NES in the US, also in 1990. Kojima was not involved in its development, which was instead conducted by another Konami team, resulting in a game that was more action based and not part of the Metal Gear canon.

Alien vs Predator, released in 1994 for the Atari Jaguar, allowed the player to become invisible and stalk enemies. 1997's PlayStation game Oddworld: Abe's Oddysee rarely required the player to combat enemies, while certain levels in first-person shooter GoldenEye 007 (released the same year) could be completed via hand-to-hand combat and the destruction of surveillance cameras.

Establishing a genre: 1998–2002
Although stealth gameplay had appeared in a several games in the 1980s and 1990s, 1998 is seen as a turning point in gaming history because of the release of Metal Gear Solid, Tenchu: Stealth Assassins, and Thief: The Dark Project. The ninja-themed game Tenchu: Stealth Assassins was released several months before Metal Gear Solid, making it the first 3D stealth based-game. The highly anticipated Metal Gear Solid transformed its modestly successful franchise into a large mainstream success. The increased power of the PlayStation console over previous platforms allowed for greater immersion in terms of both story and game environment. Metal Gear Solid has been credited with popularizing the stealth genre. Thief: The Dark Project, which featured devices such as burglary and lock-picking, is also credited as a pioneer in the stealth game genre and the first stealth game to use lighting and shadows for hiding. The core elements of these games, such as avoiding confrontation, minimizing noise, and attacking antagonists from "the shadows", influenced many future stealth game series.

With further releases, many games in the genre have drifted towards action by allowing the option of direct confrontations. The Hitman series, the first installment of which was released in 2000, allowed this play style, but rewarded the player for stealthy and elaborate assassination of antagonists. Hitman: Codename 47 was also the first 3D game to employ the genre's device of disguises. No One Lives Forever, an espionage themed parody also released in 2000, again allowed the player to combine or choose between stealth and overt violence.

The acclaimed Metal Gear series continued with Metal Gear Solid 2: Sons of Liberty (PlayStation 2; 2001) which further evolved the stealth gameplay. It featured an array of new abilities, including "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 game also introduced a collective enemy AI, where, unlike previous games in the genre, the enemy guards in Metal Gear Solid 2 work together in squads, can communicate with one another, and react in a more realistic manner towards the player. The game's enemy AI is still considered one of the finest examples in the genre. Metal Gear Solid 2: Sons of Liberty became the genre's best selling game with 7 million in sales, followed by Metal Gear Solid with 6 million in sales. They were followed by two more sequels, Metal Gear Solid 3: Snake Eater (PlayStation 2; 2004), which introduced camouflage to the genre, and Metal Gear Solid 4: Guns of the Patriots (PlayStation 3; 2008).

Later Developments: 2002-Today
2002 saw the first installment of the Tom Clancy licensed Splinter Cell series, an attempt at a more realistic game in the vein of Metal Gear. As with Metal Gear, if the player is discovered in Splinter Cell, the guards will often raise a general alarm. This can cause a difficulty spike or even result in automatic mission failure. Splinter Cell was notable for its state of the art graphics, including dynamic lighting and shadows. These effects not only contributed to the atmosphere of the game, but dynamically affected in which areas the player could hide. The 2004 sequel, Tom Clancy's Splinter Cell: Pandora Tomorrow, offered an innovative multiplayer component to the stealth genre.

Sly Cooper, a cel-shaded game released in 2002, was a "stealth platformer", while 2003's Siren combined the survival horror genre with the stealth genre. The controversial Manhunt (also 2003) employed a snuff movie theme and allowed the player to kill antagonists with varying levels of violence, dependant on how much time was spent sneaking behind them.

In 2004, The Chronicles of Riddick: Escape From Butcher Bay was released based on the Chronicles of Riddick series of movies. The game follows the character of Riddick as he attempts to escape from prison. Action and stealth gaming are combined seamlessly by allowing the character to hide, sneak, or fight his way past most situations. The game was critically acclaimed   and was followed in 2009 with The Chronicles of Riddick: Assault on Dark Athena.

In 2007, Assassin's Creed employed a social element to the stealth game, where the player is able to hide among crowds of civilians if they take care to blend in. The 2009 sequel, Assassin's Creed II broadened these elements of stealth by allowing the player to blend among any group of civilians, rather than specific ones. Assassin's Creed II also allowed the player to distract guards by tossing coins or by hiring prostitutes and featured a notoriety level, which made the player more recognizable until they paid off officials or tore down wanted posters.