Scrolling in the context of Arrow key

Shoot 'em ups (also known as shmups or STGs) are a subgenre of action games. 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, while others allow a broader definition including characters on foot and a variety of perspectives.

The genre's roots can be traced back to earlier shooting games, including target shooting electro-mechanical games of the mid-20th-century, but did not receive a video game release until Spacewar! (1962). The shoot 'em up genre was established by the hit arcade game Space Invaders, which popularised and set the general template for the genre in 1978, and has spawned many clones. The genre was then further developed by arcade hits such as Asteroids and Galaxian in 1979. Shoot 'em ups were popular throughout the 1980s to early 1990s, diversifying into a variety of subgenres such as scrolling shooters, run and gun games and rail shooters. 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. "Bullet hell" games are a subgenre of shooters that features overwhelming numbers of enemy projectiles, often in visually impressive formations.

Galaxian is a 1979 fixed shooter video game developed and published by Namco for arcades during early video games' golden age. The player assumes control of the Galaxip starfighter in its mission to protect Earth from waves of aliens. Gameplay involves destroying each formation of aliens, who dive down towards the player in an attempt to hit them.

Designed by company engineer Kazunori Sawano, Galaxian was Namco's answer to Space Invaders, a similar space shooter released the previous year by rival developer Taito. Space Invaders was a sensation in Japan, and Namco wanted a game that could compete against it. Sawano strove to make the game simple and easy to understand. He was inspired by the space combat scenes in Star Wars, with enemies originally being in the shape of the film's TIE Fighters. Galaxian is one of the first video games to feature RGB color graphics, and the first to use a tile-based hardware system, which was capable of animated multi-color sprites as well as scrolling; the latter was limited to the starfield background while the game itself remained a fixed shooter.

In the history of video games, the 3rd generation of video game consoles, commonly referred to as the 8-bit era, began on July 15, 1983, with the Japanese release of two systems: Nintendo's Family Computer (commonly abbreviated to Famicom) and Sega's SG-1000. When the Famicom was released outside of Japan, it was remodeled and marketed as the Nintendo Entertainment System (NES). This generation marked the end of the North American video game crash of 1983, and a shift in the dominance of home video game manufacturers from the United States to Japan. Handheld consoles were not a major part of this generation; the Game & Watch line from Nintendo (which started in 1980) and the Milton Bradley Microvision (which came out in 1979) that were sold at the time are both considered part of the previous generation due to hardware typical of the second generation.

Improvements in technology gave consoles of this generation improved graphical and sound capabilities, comparable to the golden age of arcade games. The number of simultaneous colors on screen and the palette size both increased which, along with larger resolutions, more sprites on screen, and more advanced scrolling and pseudo-3D effects, which allowed developers to create scenes with more detail and animation. Audio technology improved and gave consoles the ability to produce a greater variation and range of sound. A notable innovation of this generation was the inclusion of cartridges with on-board memory and batteries to allow users to save their progress in a game, with Nintendo's The Legend of Zelda introducing the technology to the worldwide market. This innovation allowed for much more expansive gaming worlds and in-depth storytelling, since users could now save their progress rather than having to start each gaming session at the beginning. By the next generation, the capability to save games became ubiquitous—at first saving on the game cartridge itself and, later, when the industry changed to read-only optical disks, on memory cards, hard disk drives, and eventually cloud storage.

Scramble is a 1981 horizontally scrolling shooter video game developed and published by Konami for arcades. It was distributed by Leijac for manufacture in Japan and Stern in North America. It was the first side-scrolling shooter with forced scrolling and multiple distinct levels, and it established the foundation for a new genre.

It was Konami's first major worldwide hit. In the United States, it sold 15,136 arcade cabinets within five months and became Stern's second best-selling game. Scramble was not ported to any major contemporary consoles or computers, but there were releases for the Tomy Tutor and Vectrex as well as dedicated tabletop/handheld versions. Unauthorized clones for the VIC-20 and Commodore 64 use the same name as the original.