Shoot 'em up video games

Shoot 'em up video games (also known as shmups or STG) is a sub-genre of the shooter genre of video games. Shoot 'em ups, have the player control a lone character (or vehicle) whose objective is to destroy waves upon waves of enemies while dodging their attacks. Shoot 'em ups are action video games that characteristically feature either a top-down or horizontal view. There is no consensus as to which design elements compose a shoot 'em up. Some restrict the definition to games featuring spacecraft and certain types of character movement; others allow a broader definition including characters on foot and a variety of perspectives. Shoot 'em ups are known for their fast-paced action, often having dizzying amounts of bullets and enemies on the screen and call for the player to memorize levels and enemy attack patterns. "Bullet hell" games feature overwhelming numbers of enemy projectiles. Shoot 'em ups are generally considered to be one of the most difficult genres of video games. Popular sub-genres include side-scrolling shooters and Run & Gun video games.

The genre's origins can be traced back to Spacewar!, one of the earliest computer games, developed in 1962 and eventually released in amusement arcades in the early 1970s. However, Tomohiro Nishikado, creator of Space Invaders, is generally credited with inventing the genre. Space Invaders premiered in Japanese arcades in 1978. Shoot 'em ups were popular throughout the 1980s and early 1990s. In the mid-1990s, shoot 'em ups became a niche genre based on design conventions established in the 1980s, and increasingly catered to specialist enthusiasts, particularly in Japan.

Definition
A "shoot 'em up", also known as a "shmup" or "STG", is a game in which the protagonist combats a large number of enemies by shooting at them while dodging their fire. The controlling player must rely primarily on reaction times to succeed. Beyond this, critics differ on exactly which design elements constitute a shoot 'em up. Some restrict the genre to games featuring some kind of craft, using fixed or scrolling movement. Others widen the scope to include games featuring such protagonists as robots or humans on foot, as well as including games featuring "on-rails" (or "into the screen") and "run and gun" movement. Formerly, critics described any game where the primary design element was shooting as a "shoot 'em up", but later shoot 'em ups became a specific, inward-looking genre based on design conventions established in those shooting games of the 1980s.

Common elements
Shoot 'em ups are a sub-genre of shooter video games, in turn a type of action video game. These games are usually viewed from a top-down or side-view perspective, and players must use ranged weapons to take action at a distance. The player's avatar is typically a vehicle under constant attack. Thus, the player's goal is to shoot as quickly as possible anything that moves or threatens him. In some games, the player's character can withstand some damage; in others, a single hit will result in his destruction. The main skills required in shoot 'em ups are fast reactions and memorising enemy attack patterns. Some games feature overwhelming numbers of enemy projectiles and the player has to memorise their patterns to survive plus boss fights can be defeated at the end of the levels or at some point. These games belong to one of the fastest-paced video game genres.

Large numbers of enemy characters are typically featured. These enemies may behave in a certain way dependent on their type, or attack in formations that the player can learn to predict. The basic gameplay tends to be straightforward and many games offset this with a variety of weapons. Shoot 'em ups rarely have realistic physics. Characters can instantly change direction with no inertia, and projectiles move in a straight line at constant speeds. The player's character can collect "power-ups" which may afford the character greater protection, an "extra life", or upgraded weaponry. Different weapons are often suited to different enemies, but these games seldom keep track of ammunition. As such, players tend to fire indiscriminately, and their weapons only damage legitimate targets.

Types
Shoot 'em ups are categorised by design elements, particularly viewpoint and movement:

"Fixed shooters" consist of levels that each fit within a single screen. The protagonist's movement is fixed to a single axis of motion, and enemies attack in a single direction (such as descending from the top of the screen). These games are sometimes also called "gallery shooters".

"Rail shooters" limit the player to moving around the screen while the game follows a specific route; these games often feature an "into the screen" viewpoint, with which the action is seen from behind the character. The term "rail shooter" is also often applied to light gun shooters that use "on-rails" movement, and the term has also been applied to linear first-person shooters such as Call of Duty in recent years.

"Tube shooters" feature craft flying through an abstract tube.

"Scrolling shooters" include vertical or horizontal scrolling games. In a vertically scrolling shoot 'em up (or "vertical scroller"), the action is viewed from above and scrolls up (or very occasionally down) the screen. This has the advantage of allowing complex patterns of enemies, as well as allowing even simple graphics to function convincingly. Vertical scrollers are best suited for arcade machines with tall screens; screens used with home computers or consoles tend to be wider than they are tall, thus are less suited to vertical scrolling. The other main type of scrolling shooter is a "horizontal shooter" or "side-scrolling shooter", in which the action is viewed side-on and scrolls horizontally. A small number of scrolling shooters, such as SEGA's Zaxxon, feature an isometric point of view.

Others dispense with scrolling altogether, instead using a flip-screen device: when a player reaches the edge of the screen, a whole new scene appears at once. Some shooters may feature multi-directional movement ("multidirectional shooter"), generally with a static screen.

"Bullet hell" (弾幕) is a shoot 'em up in which the entire screen is often almost completely filled with enemy bullets. This type is also known as "curtain fire", "manic shooters" or "maniac shooters". This style of game originated in the mid-1990s, and is an offshoot of scrolling shooters.

"Cute 'em ups" feature brightly coloured graphics depicting surreal settings and enemies. Newer, particularly Japanese, cute 'em ups employ overtly sexual characters and innuendo.

"Run & Gun" (or "run 'n gun") describes a shoot 'em up in which the protagonist fights on foot, perhaps with the ability to jump. Run & gun games may use side-scrolling, vertical scrolling or isometric viewpoints and may feature multidirectional movement. These types of games may also be termed "scrolling shooters".

Origins and rise
The genre's exact origins are a matter of some confusion. Video game journalist Brian Ashcraft pinpoints Spacewar! (one of the very earliest computer games) as the first shooter, but the later Space Invaders is more frequently cited as the "first" or "original" in the shoot 'em up genre. Spacewar! was developed at the Massachusetts Institute of Technology in 1961, for the amusement of the developers; it was, however, remade four times as an arcade game in the early to mid-1970s. The game featured combat between two spacecraft. Such games based on one-on-one combat are sometimes classified as "combat games" rather than "shooter" or "shoot 'em up" games, which are usually based on shooting at multiple opponents (the "'em" being shorthand for "them") attacking at once.

From the mid-1970s, Taito released several experimental shooting games that culminated in their seminal title Space Invaders. In 1975, they released Western Gun (Gun Fight), designed by Space Invaders creator Tomohiro Nishikado. It was an early two-player, on-foot, multidirectional shooter, which was also the first video game to depict a gun on screen, introduced dual-stick controls with one eight-way joystick for movement and the other for changing the shooting direction, and was the first known video game to feature game characters and fragments of story through its visual presentation. That same year, they released Interceptor, also designed by Nishikado. It was an early first-person combat Flight simulator that involved piloting a jet fighter, using an eight-way joystick to aim with a crosshair and shoot at enemy aircraft that move in formations of two and scale in size depending on their distance to the player. In 1977, Taito released Missile-X, a simulator that featured real-life colour images as background scenery, and involved the player launching missiles to destroy enemy tanks, and Sub Hunter, an early submarine simulator that featured colour background scenery and involved controlling a destroyer that fires depth charges at submarines while having to avoid their mines. That same year, SEGA released an early side-scrolling video game for the arcades, Bomber, which involved controlling a bomber plane that drops bombs on moving targets, which include a scrolling pattern of buildings, while shooting at oncoming fighter jets that also move in a scrolling pattern across the screen.

However, it was not until 1978's seminal Space Invaders, created by Nishikado at Japan's Taito Corporation, that the shooter genre became prolific. Space Invaders pitted the player against multiple enemies descending from the top of the screen at a constantly increasing rate of speed. The game used alien creatures because the developers were unable to render the movement of aircraft; in turn, the aliens replaced human enemies because of moral concerns (regarding the portrayal of killing humans) on the part of Taito Corporation. As with subsequent shoot 'em ups of the time, the game was set in space as the available technology only permitted a black background. The game also introduced the idea of giving the player a number of "lives". Space Invaders was a massive commercial success, causing a coin shortage in Japan, and gaining mainstream popularity in America. It popularized a more interactive style of gameplay with the enemies responding to the player-controlled cannon's movement, and it was the first video game to popularize the concept of achieving a high score,  being the first to save the player's score. While earlier shooting games allowed the player to shoot at targets, Space Invaders was the first in which targets could fire back at the player. It was also the first game where players had to repel hordes of enemies, take cover from enemy fire, and use destructible barriers, in addition to introducing a continuous background soundtrack. It set the template for the shoot 'em up genre, and has influenced most shooting games released since then. That same year, SEGA released an early vector graphics space combat game, Space Ship, where two players battle to destroy each other, and Secret Base, which allowed two-player co-operative gameplay and where the aim was to destroy an enemy base amidst enemy missiles and anti-aircraft fire.

Golden age and refinement
In 1979, Space Invaders Part II introduced RGB colour graphics to the genre as well as the concept of a cutscene. It also introduced the concept of secret hidden bonuses, where shooting columns of invaders from the top down rewarded extra points. The same year, Namco's Galaxian took the genre further with more complex enemy patterns and richer graphics, and the popularization of colour graphics. It featured an improved enemy AI, where enemy ships frequently break out of formation to dive towards the player, making it the first game to feature enemies with individual personalities. Namco also released SOS, the first vertical scrolling shooter. That same year saw the release of SNK's debut shoot 'em up Ozma Wars, also an early vertical scrolling shooter, notable for being the first action game to feature a supply of energy, resembling a life meter, a mechanic that has now become common in the majority of modern action games. Konami also developed Kamikaze, a fixed-shooter where the aliens can plummet to the Earth, causing an explosion that could kill the player if nearby. It was released by Stern as Astro Invader the following year. Nintendo's Sheriff (designed by Shigeru Miyamoto), released in 1979, was a run & gun multi-directional shooter that featured dual-stick controls, with one joystick for movement and the other for aiming, and a large number of enemies shooting many bullets, paving the way for dual-stick shooters such as Robotron: 2084 and later Geometry Wars. Nintendo also released Radar Scope (also designed by Shigeru Miyamoto), which introduced a three-dimensional third-person perspective, imitated years later by shooters such as Konami's Juno First and Activision's Beamrider.

In 1980, SEGA released Carnival, an early shooting gallery game with a bonus round, and Space Tactics, featuring a first-person perspective, the player having to defend five bases, a shield with limited renewal capability available to protect the bases, each base capable of firing a large single shot, the alien ships attacking in a 3D pattern towards the screen, the entire screen mobilizing and scrolling in multiple directions as the player moves the cross-hairs, and a laser that shoots into the screen, creating a real-life 3D effect. Space Firebird, developed by Nintendo and published by SEGA-Gremlin, featured a special warp button that gave the player temporary invincibility. Other notable games from that year include Sun's Stratovox, a simple fixed-shooter best known for being the first video game to introduce speech synthesis, and SNK's Sasuke vs Commander, a fixed-shooter that featured human characters instead of spaceships, specifically shuriken-throwing ninjas, as well as boss encounters, against shinobi with abilities such as shooting flame. That same year, Moon Cresta featured vertical scrolling backgrounds.

In February 1981, side-scrolling was popularized by two major releases: Defender  and Scramble. Defender offered horizontally extended levels, and unlike most later games in the genre, the player could move in either direction. The game's use of scrolling helped remove design limitations associated with the screen, and though the game's minimap feature had been introduced before, Defender integrated it into the gameplay in a more essential manner. Meanwhile, Konami's Scramble was the first side-scolling shooter with forced scrolling, and it was the first scrolling shooter to offer multiple, distinct levels. The game's forced scrolling became the basis for most subsequent shmups. 1981 also saw the release of Jump Bug, a scrolling platform-shooter where players controlled a car and featured levels that scrolled both horizontally and vertically. SNK's second scrolling shooter Vanguard was also released that year, and it was both a horizontal and vertical scrolling shooter that allowed the player to shoot in four directions. It was also an early dual-control game, similar to the later multi-directional shooter Robotron 2084, but using four directional buttons rather than a second joystick. Atari's Tempest, released in 1981, is one of the earliest tube shooters and an early attempt to incorporate a 3D perspective into shooter games. Tempest ultimately went on to influence major rail shooters. That same year, Taito released Space Seeker, a shooter that allowed the player to choose which level to play, some of which were side-scrolling while others were viewed from a first-person perspective. SEGA's Eliminator was notable for its colour vector graphics, competitive and co-operative gameplay, and for being the only four-player vector game ever released, while SEGA's Space Fury that year also featured colour vector graphics in addition to speech synthesis. Hoei's Mayday!! was inspired by Defender but added several new features, including an eight-direction joystick, a Mayday button that enables slow motion for five seconds, being able to speed up and slow down the ship's forward momentum, and the ability to crash into cavern walls. Namco's Bosconian introduced a free-roaming style of gameplay where the player's ship could freely move across open space that scrolls in all directions and a radar that tracks the positions of the player and enemies on the map. Taito's Space Dungeon also featured an automap to keep track of the player's movement from screen to screen; the game also featured gameplay and dual-stick controls similar to Robotron 2084 and Smash TV. Other notable shooters released that year were Namco's Galaxian successor Galaga, one of the first games with a bonus stage, and Universal's Snap Jack, a scrolling shooter that was a cross between Scramble and Pac-Man.

Vertical scrolling shooters emerged around the same time. Namco's Xevious, released in 1982, is frequently cited as the first vertical shooter and, although it was de facto preceded by several other games featuring vertical scrolling (most notably Nihon Bussan's Missile-X  in early 1982 ), it was the most influential. Xevious is also the first to convincingly portray realistic landscapes as opposed to purely science fiction settings. That same year, Irem's Moon Patrol is a side-scrolling shooter that introduced the use of parallax scrolling to give an early pseudo-3D effect. While Asteroids (1979) allowed the player to rotate the game's spacecraft, 1982's acclaimed Robotron: 2084 was one of the most influential on subsequent multi-directional shooters. That same year, several early vertical-scrolling run & gun shooters were released, including Taito's Front Line, an early military-themed multi-directional shooter to have players control foot soldiers rather than vehicles, Taito's Wild Western, where the player character on a horse must defend a moving train from robbers, and Jaleco's Naughty Boy, about a boy who throws rocks at monsters to destroy them, with the longer the fire button held down, the farther the character can throw rocks, while featuring boss encounters and bonus rounds. That year, Kaneko also released the Namco Galaxian game Red Clash, a space shooter that allowed moving and scrolling in all four directions, while SEGA released Tac/Scan, where the early overhead levels scrolled in all directions while later levels were in third-person perspective, SubRoc-3D, an early stereoscopic 3-D shooter played from a first-person perspective, and Buck Rogers: Planet of Zoom, a third-person rail shooter with fast pseudo-3D scaling and detailed sprites. Nichibutsu also released Star Attack, a scrolling shooter where shooting ships increments the time counter and which featured a "Freeze" button that stopped everything except the player's ship, while Konami released Time Pilot, which featured a time travel theme and a free-roaming style of gameplay where the player's plane could freely move across open air space that scrolls indefinitely in all directions. Also in 1982, Konami's Tutankham combined maze gameplay with multi-directional shooter gameplay, giving the game a more action-adventure feel.

In 1983, Taito released Bio-Attack, a vertical-scrolling shooter where the player controls a microscopic ship through a human body while shooting bacteria, and Sesame Japan released Vastar, a side-scrolling shooter where the player controls a mecha robot. That same year, Nippon produced Ambush, an early spaceship shooter played entirely from a third-person perspective, Technosoft released Thunder Force, an overhead shooter that allowed the player to freely scroll in any direction, and SEGA released Astron Belt, an early first-person shooter and the first arcade laserdisc game to be developed, featuring live-action footage (largely borrowed from a Japanese science fiction film) over which the player/enemy ships and laser fire are superimposed. Konami's Mega Zone was a vertical-scrolling shooter that introduced non-linear gameplay in the form of multiple different branching paths. That same year also saw the release of Enix's Kagirinaki Tatakai, an early run & gun shooter for the Sharp X1 computer that featured fully destructible environments, a convincing physics engine, and a choice of several different weapons. That same year also saw the release of another early run & gun shooter for the Sharp X1, Hover Attack, which freely scrolled in all directions, allowed the player to shoot diagonally as well as straight ahead, and let the player fire in any direction independent of the direction the character is moving. Hover Attack is known for inspiring the later more famous Bangai-O. The following year, Game Arts released Thexder, a breakthrough title for run & gun shooters. That same year, Irem released The Battle-Road, an early open-ended vehicle combat shooter that featured branching paths and up to 32 possible routes. Also in 1985, Konami released Rush'n Attack, also known as Green Beret,  one of the first  side-scrolling ,  run &amp; gun   shooters, paving the way for franchises such as  Contra ,  Bionic Commando , and  Metal Slug.

SEGA's Space Harrier, a rail shooter released in 1985, broke new ground graphically and its wide variety of settings across multiple levels gave players more to aim for than high scores. It was one of the first arcade games to use 16-bit graphics and SEGA's "Super Scaler" technology that allowed pseudo-3D sprite-scaling at high frame rates, with the ability to scale as many as 32,000 sprites and fill a moving landscape with them. It was also an early example of a third-person shooter. 1985 also saw the release of Konami's Gradius, which gave the player greater control over the choice of weaponry, thus introducing another element of strategy. The game also introduced the need for the player to memorise levels in order to achieve any measure of success. Gradius, with its iconic protagonist, defined the side-scrolling shoot 'em up and spawned a series spanning several sequels. The game's key mechanic of collectible power-ups (where certain enemies dropped power-ups ranging from increased shooting power and extra weapons to a drone that followed the player ship) was considered an important breakthrough, as it influenced many subsequent shooters.

The following year, 1986, saw the emergence of one of SEGA's forefront series with its game Fantasy Zone. The game received acclaim for its surreal graphics and setting and the protagonist, Opa-Opa, was for a time considered SEGA's mascot. The game borrowed Defender's device of allowing the player to control the direction of flight and along with the earlier Twinbee (1985), is an early archetype of the "cute 'em up" sub-genre. 1986 also saw the release of Square's medieval fantasy shooter King's Knight, which featured four characters, one per stage, where the player must keep them alive before they join to face the final boss; when a character dies prematurely, it's a permanent death, and the game shifts to the next character in their own stage. Taito's Darius featured a unique three-screen arcade cabinet and a non-linear level design where the player is given a choice of which path to follow after each boss; out of 28 possible stages, the player would only be able to play through seven at most during each run through the game. Silpheed, a forward-scrolling third-person space combat game by Game Arts, was an early example of a fully 3D polygonal shooter. R-Type, an acclaimed side-scrolling shoot 'em up, was released in 1987 by Irem, employing slower paced scrolling than usual, with difficult levels calling for methodical strategies. 1990's Raiden was the beginning of another acclaimed and enduring series to emerge from this period.

Shoot 'em ups such as SNK's Ikari Warriors (1986) featuring characters on foot, rather than spacecraft, became popular in the mid-1980s in the wake of action movies such as Rambo: First Blood Part II (1985). The first game of this type is uncertain but the first influential example is Commando, released in 1985. Commando also drew comparisons to Rambo and indeed contemporary critics considered military themes and protagonists similar to Rambo or Schwarzenegger prerequisites for a shoot 'em up, as opposed to an action-adventure game. In 1986, Arsys Software released WiBArm, a shooter that switched between a 2D side-scrolling view in outdoor areas to a fully 3D polygonal third-person perspective inside buildings, while bosses were fought in an arena-style 2D battle, with the game featuring a variety of weapons and equipment. In 1987, Square's 3-D WorldRunner was an early stereoscopic 3-D shooter played from a third-person perspective, followed later that year by its sequel JJ, and the following year by Space Harrier 3-D which used the SEGAScope 3-D shutter glasses. That same year, SEGA's Thunder Blade switched between both a top-down view and a third-person view, and introduced the use of force feedback, where the joystick vibrates. Also in 1987, Konami created Contra as an coin-op arcade game that was particularly acclaimed for its multi-directional aiming and two player cooperative gameplay. However, by the early 1990s and the popularity of 16-bit consoles, the scrolling shooter genre was overcrowded, with developers struggling to make their games stand out (one exception being the inventive Gunstar Heroes, by Treasure).

"Bullet hell" evolution and niche appeal
A new type of shoot 'em up emerged in the early 1990s: variously termed "bullet hell", "manic shooters" and "maniac shooters", these games required the player to dodge overwhelming numbers of enemy projectiles and called for still faster reactions from players. Bullet hell games arose from the need for 2D shoot 'em up developers to compete with the emerging popularity of 3D games: huge numbers of missiles on screen were intended to impress players. Toaplan's Batsugun (1993) provided the prototypical template for this new breed, with Cave (formed by former employees of Toaplan, including Batsugun's main creator Tsuneki Ikeda, after the latter company collapsed) inventing the type proper with 1995's DonPachi. Manic shooter games marked another point where the shoot 'em up genre began to cater to more dedicated players. Donpachi was followed by two manic shooters developed by Raizing/Eighting: Battle Garegga and Terra Diver. Games such as Gradius had been more difficult than Space Invaders or Xevious, but bullet hell games were yet more inward-looking and aimed at dedicated fans of the genre looking for greater challenges. While shooter games featuring protagonists on foot largely moved to 3D-based genres, popular, long-running series such as Contra and Metal Slug continued to receive new sequels. Rail shooters have rarely been released in the new millennium, with only Rez and Panzer Dragoon Orta achieving cult recognition.

Treasure's shoot 'em up, Radiant Silvergun (1998), introduced an element of narrative to the genre. It was lavished with critical acclaim for its refined design, though it was never released outside of Japan and remains a much sought after collectors' item. Its successor Ikaruga (2001) featured improved graphics and was again acclaimed as one of the best games in the genre. Both Radiant Silvergun and Ikaruga were later released on Xbox Live Arcade. The Touhou Project series is another notable example of the bullet hell game. The project spans fifteen years and nineteen games as of 2011. It was listed in the Guinness World Records in October 2010 for being the "most prolific fan-made shooter series". The genre has undergone something of a resurgence with the release of the Xbox 360, Playstation 3 and Wii online services, while in Japan arcade shoot 'em ups retain a deep-rooted niche popularity. Geometry Wars: Retro Evolved was released on Xbox Live Arcade in 2005 and in particular stood out from the various re-releases and casual games available on the service. However, despite the genre's continued appeal to an enthusiastic niche of players, shoot 'em up developers are increasingly embattled financially by the power of home consoles and their attendant genres. A modern developer known for specializing in arcade bullet hell shooters is Cave. Their recent arcade game Akai Katana was ported to the Xbox 360 and released to critical acclaim.