Space Invaders
is a 1978 shoot 'em up video game developed and published by Taito for arcades. It was released in Japan in April 1978, and released overseas by Midway Manufacturing later that year. Space Invaders was the first video game with endless gameplay and the first fixed shooter, setting the template for the genre. The goal is to defeat waves of descending aliens with a horizontally moving laser cannon to earn as many points as possible.
Designer Tomohiro Nishikado drew inspiration from video games such as Gun Fight and Breakout, electro-mechanical target shooting games, and science fiction narratives such as the novel The War of the Worlds, the anime Space Battleship Yamato, and the film Star Wars. To complete development, he had to design custom hardware and development tools to use the features in microprocessor technology, which was new to him. Upon release, Space Invaders quickly became a commercial success worldwide; by 1982, it had grossed , with a net profit of . This made it the best-selling video game and highest-grossing entertainment product at the time, and the highest-grossing video game yet.
Space Invaders is considered one of the most influential and greatest video games ever, having ushered in the golden age of arcade video games and Japan's long-lasting global success in the video games industry. It inspired several prolific game designers to join the industry and influenced numerous games across different genres. The game has been ported and re-released in various forms, including the 1980 Atari 2600 version, which quadrupled sales of the Atari 2600 console and became the first killer app for video game consoles. The pixelated enemy alien has become a pop culture icon, often representing video games as a whole. The game has spawned dozens of sequels and remakes, been the inspiration for numerous pieces of art and music, been parodied across media, and been the focus of several pieces of legislation to limit access to video games.
Gameplay
Space Invaders is a fixed shooter in which the player moves a laser cannon, referred to as a "Laser Base", horizontally across the bottom of the screen and fires at a group of the titular alien invaders overhead. The invaders begin as five rows of eleven—the amount differs in some versions—that move left and right as a group, advancing on the shooter by shifting downward each time they reach a screen edge. The goal is to eliminate all the invaders by shooting them. Regardless of how many game lives remaining the player has, the game ends if the aliens reach the bottom of the screen.The aliens attempt to destroy the player's cannon by firing projectiles. The laser cannon is partially protected by stationary defense bunkers that are gradually destroyed from above by the invaders; the bottom will be destroyed if the player fires when beneath one. As the invaders are defeated, their movement, as well as the accompanying music, speeds up. Defeating all the aliens brings another wave that starts lower, a loop that can continue endlessly. A special "mystery ship" will occasionally move across the top of the screen and award bonus points if destroyed.
Development
Space Invaders was developed by Japanese designer Tomohiro Nishikado, who spent a year designing it and developing the necessary hardware to produce it. Because he worked alone and handmade many of the development tools, the process incurred minimal costs. Taito originally did not credit a designer as anonymity was a required part of Nishikado's contract with the company.The game was a response to Atari, Inc.'s 1976 arcade game Breakout. Nishikado noted that Breakout-style games were very popular in Japan in 1977. He was a fan of the game and aimed to create something better. The developer wanted to adapt the same sense of achievement and tension from destroying targets one at a time, combining it with elements of target shooting games. The game uses a similar layout to that of Breakout but with different game mechanics; rather than bounce a ball to attack static objects, players are given the ability to fire projectiles at moving enemies.
To improve the design, Nishikado felt the targets should have an interesting shape. Early enemy designs included tanks, combat planes, and battleships. Nishikado was not satisfied with the enemy movements; technical limitations made it difficult to animate flying. The designer believed animating human characters would have been easier to program, but he considered shooting them immoral. Nishikado also said that shooting people was frowned upon. After seeing the release of the 1974 anime Space Battleship Yamato in Japan, and seeing a magazine feature about the 1977 Star Wars, he thought of using a space theme. Nishikado drew inspiration for the aliens from the novel The War of the Worlds and created initial bitmap images after the octopus-like aliens. Other alien designs were modeled after squids and crabs. After creating the pixel art, Nishikado created a tool to animate two frames of movement for each character and adjusted the design on-screen with a light pen. He added the bunkers and the mystery ship to the playing field afterward.
Nishikado added several interactive elements that he found lacking in earlier video games, such as enemies reacting to the player's movement and returning fire, and a game over triggered by the enemies killing the player character rather than simply a timer running out. He replaced the timer, typical of arcade games at the time, with descending aliens who effectively served a similar function, where the closer they came, the less time remained for the player. During the process, Nishikado wanted the game's difficulty to increase the longer the game progressed; he reasoned this kept the gameplay fresh and that the game would earn less if players could play for extended periods. He relied on feedback from his coworkers to balance the difficulty; in retrospect, Nishikado stated that without their input he would have made the game less challenging because he struggled to play it. The game was originally titled Space Monsters after a popular song in Japan at the time, "Monster", but was changed to Space Invaders by the designer's superiors.
Hardware
Nishikado designed his own custom hardware and development tools for Space Invaders. The game uses an Intel 8080 central processing unit and displays raster graphics on a CRT monitor using a bitmapped framebuffer. The game outputs monaural sound hosted by a combination of analog circuitry and a Texas Instruments SN76477 sound chip.The adoption of a microprocessor was inspired by the 1975 arcade game Gun Fight, Midway's microprocessor adaptation of Nishikado's earlier discrete logic game Western Gun, after the designer was impressed by the improved graphics and smoother animation of Midway's version. At the time, Taito had licensed Midway's technology to use in its games. Nishikado used Midway's arcade board as a motherboard and created additional boards and circuitry to expand the capabilities.
As microprocessors were manufactured in the United States, Nishikado had to rely on his English skills, which he described as limited, to translate the reference material. He dedicated about six months to studying American games and mastering using a microcomputer. While planning the game, Nishikado made iterative improvements to the hardware. He attributes his previous experience working with integrated circuits and learning assembly language during his university studies with helping him learn how to interact with the new hardware.
To add audio, Nishikado worked with Michiyuki Kamei, who created sound effects for Taito's games. Kamei spent four to five months on the audio circuitry for Space Invaders while also working on another game, Blue Shark. As management had prioritized Blue Shark, his work on Space Invaders was hurried in order to have both games ready for an unveiling event in the summer of 1978. Kamei decided to reuse parts and designs from other Taito games to meet the deadline. He replaced resistors and capacitors to adjust the pitch and duration of sound effects he created for Blue Shark. To create the invaders' moving sound effect, Kamei reused the 556 timer integrated circuit from Super Speed Race. Kamei felt the first invader sound effects were too comical and changed it after seeing the monster on the cabinet artwork and receiving feedback from Nishikado. Aiming to emulate the Jaws shark theme, he added resistors to the circuit in order to lower the effect's pitch. Texas Instruments had recently provided Taito free samples of the SN76477 sound chip, which Kamei inspected. Despite the higher cost, he chose it to produce the mystery ship's sound effects because the smaller chip saved space on the board.
Despite the specially developed hardware, Nishikado was unable to program the game as he wanted—the Control Program board was not powerful enough to display the graphics in color or move the enemies faster—and considered the development of the hardware the most difficult part of the process. While programming, Nishikado discovered that the processor was able to render each frame of the alien's animation graphics faster when there were fewer aliens on the screen. Since the alien's positions updated after each frame, this caused the aliens to move across the screen at an increasing speed as more were destroyed; the accompanying audio sped up as well. Rather than design a compensation for the speed increase, he decided to keep this undocumented feature as a gameplay mechanism. In retrospect, Nishikado noted that this aspect made the game more interesting and compensated for the hardware's limitations.
The cabinet artwork features large humanoid monsters absent from the game, which Nishikado attributed to the artist basing the designs on the original "Space Monsters" title rather than referring to the in-game graphics. In the upright cabinets, the graphics are generated on a hidden CRT monitor and reflected toward the player using a semi-transparent mirror, behind which is mounted a plastic cutout of a moon bolted against a painted starry background. The backdrop is visible through the mirror and thus appears "behind" the graphics. Both Taito's and Midway's first Space Invaders releases have black-and-white graphics with strips of transparent orange and green cellophane over certain portions of the screen to add color to the image. Later Japanese releases feature a rainbow-colored cellophane overlay; later versions had a color monitor and an electronically generated color overlay.