Spacewar! is a space combat video game created in 1962 by Steve Russell with help from Martin Graetz, Wayne Wiitanen, Bob Saunders, Steve Piner, and others. It was developed for the DEC PDP-1 minicomputer at the Massachusetts Institute of Technology. After its first creation, Spacewar! was improved by students and workers at nearby universities, including Dan Edwards and Peter Samson. The game was also shared with other PDP-1 computers, making it the first video game known to be played on multiple computers.
The game includes two spaceships, "the needle" and "the wedge," fighting in a star's gravity well. Players control both ships. Each ship has limited weapons and fuel, and they keep moving even when not accelerating. Using the star's gravity to help move was a common strategy. Ships are destroyed if they hit a torpedo, the star, or each other. Players can use a "hyperspace" feature to jump to a random location on the screen, though some versions increase the risk of destroying the ship with each use. The game was first played using switches on the PDP-1, but Bob Saunders created an early gamepad to make it easier to control.
Spacewar! is one of the most important and influential games in early video game history. It was very popular among programmers in the 1960s, and its public domain code was widely copied and adapted on other computers, especially after monitors became more common in the late 1960s. The game has also been recreated in modern programming languages for PDP-1 emulators. It directly inspired early commercial arcade games, such as Galaxy Game and Computer Space (both from 1971), and later games like Asteroids (1979). In 2007, Spacewar! was listed as one of the ten most important video games in history, marking the start of the game canon at the Library of Congress. In 2018, it was added to the World Video Game Hall of Fame by The Strong and the International Center for the History of Electronic Games.
Background
During the 1950s, computer games were developed as part of research on computers and programming. These games were often created to show how powerful computers could be, especially after smaller and faster computers became available. These new computers allowed programs to run in real time instead of following a schedule. Some games were made to both demonstrate computer power and provide entertainment. These games were usually created by students and university workers, such as those at the Massachusetts Institute of Technology (MIT). At MIT, staff and students sometimes used the TX-0 experimental computer to develop programs. These interactive games were made by a group of programmers, many of whom were students or employees connected to the Tech Model Railroad Club (TMRC). Key members of this group included Alan Kotok, Peter Samson, and Bob Saunders. Examples of these games included Tic-Tac-Toe, which used a light pen to play a simple game of noughts and crosses against the computer, and Mouse in the Maze, which used a light pen to create a maze for a virtual mouse to navigate.
In September 1961, a Digital Equipment Corporation (DEC) PDP-1 minicomputer was placed in a special room on the second floor of Building 26, which housed the MIT Electrical Engineering Department. The PDP-1 was meant to work alongside the older TX-0 computer. Like the TX-0, it had a device to read and write punched tape. It also accepted input from a panel of switches and could display information on a cathode-ray tube (CRT) screen. Before the PDP-1 arrived, a group of students and university workers had been thinking about programs that could show the computer’s abilities in an engaging way. Three individuals—Steve Russell, who was then working at Harvard University and had previously been a research assistant at MIT; Martin Graetz, a research assistant and former student at MIT; and Wayne Wiitanen, a research assistant at Harvard and former student and employee at MIT—developed the idea for Spacewar!. They called their collaboration the "Hingham Institute" because Graetz and Wiitanen lived in a building on Hingham Street in Cambridge, Massachusetts. In a 1972 interview with Rolling Stone, Steve Russell said, "We had this brand new PDP-1. Someone had made some simple programs that created interesting patterns, like a kaleidoscope. Not a very good demonstration. Here was this display that could do all sorts of good things! So we started talking about it, thinking about what would make an interesting display. We decided that probably you could make a two-dimensional maneuvering game, and naturally, the obvious idea was spaceships."
Gameplay
The game Spacewar! features two black-and-white spaceships, called "the needle" and "the wedge," each controlled by a player. The goal is to shoot the other ship while moving on a flat surface near a star's gravity. The background shows a starfield. Players fire torpedoes, which are not pulled by the star's gravity. Each ship has a limited number of torpedoes and fuel, which is used when players push the ship's thrusters. Torpedoes are fired one at a time by pressing a switch on the computer or a button on the control pad. There is a waiting time between each torpedo launch. The ships keep moving even when players stop accelerating, and turning the ships does not change their direction, though they can spin continuously without slowing down.
Each player must try to destroy the other ship while avoiding crashing into the star or the opponent. Moving close to the star can help a player gain speed, but it risks crashing into the star. If a ship moves off one side of the screen, it appears on the opposite side. A feature called "hyperspace" allows a player to escape enemy torpedoes by teleporting the ship to a random spot on the screen. However, the ship may reappear in a dangerous location, and some versions increase the chance of the ship exploding with each use.
Players control the ships using options like turning left or right, moving forward, firing torpedoes, and using hyperspace. Early versions used switches on the PDP-1 computer, but these were hard to use and caused problems, such as accidentally turning off the computer. One player was also positioned far from the screen, making it harder to play. To fix these issues, a separate control device, similar to an early gamepad, was created. The gamepad had buttons for turning, moving forward, firing torpedoes, and using hyperspace. The torpedo button was silent to prevent the other player from hearing when a torpedo was fired.
Development
Russell, Graetz, and Wiitanen created the basic idea for the game Spacewar! in the summer of 1961, while waiting for the PDP-1 computer to be installed. Russell had just finished reading the Lensman series by E. E. "Doc" Smith and thought the stories would be a good inspiration for the program. He described how the stories often showed heroes escaping danger by using their creativity. These ideas helped shape the action in Spacewar!. Other influences, according to programmer Martin Graetz, included E. E. Smith’s Skylark novels and Japanese tokusatsu films.
After the PDP-1 was installed, the programming community at MIT focused on simpler programs to learn how to use the computer. During this time, Russell often visited his friends in the community and shared his Spacewar! idea. He hoped someone else would create the game, but others believed he was the best person for the task and encouraged him to take it on. Russell made excuses, such as saying the computer lacked a math function needed to calculate spacecraft movement. This led Alan Kotok of the TMRC to contact DEC, who confirmed the function was already available. Kotok brought the code to Russell, who then began working on the game after the PDP-1’s display was installed in December 1961.
Russell, Graetz, and Wiitanen wanted the game to be both fun for players and a good demonstration for others. They set three goals: use as much of the computer’s power as possible, keep the game interesting with each play, and make it entertaining. With help from other programmers, including Bob Saunders and Steve Piner, Russell spent about 200 hours writing the first version of Spacewar! in the PDP-1’s assembly language.
By the end of January 1962, Russell had a program with a movable dot. By February, he had created a working version with rotatable spaceships that resembled designs from Buck Rogers stories and the PGM-11 Redstone rocket. A randomly generated star field was added to help players see movement at slow speeds. The programming community, including groups like the Hingham Institute and TMRC, shared programs freely, leading to improvements on Russell’s game.
Peter Samson of the TMRC disliked the inaccurate star field and created a program called "Expensive Planetarium," which used real star charts to display stars in a specific sky region. Russell added this to the game in March 1962.
The first version of Spacewar! did not include a gravity well or a hyperspace feature. These were added later by Dan Edwards and Graetz to make the game more strategic. Russell had wanted gravity but faced technical challenges until Edwards improved the program’s efficiency. The initial hyperspace function allowed only three jumps, but later versions increased the risk of destroying the ship. In March 1962, Saunders created gamepads to reduce strain from using the computer’s controls.
The game was multiplayer-only because the computer lacked resources to control a second ship. Other planned features, like better explosions or gravity-affected torpedoes, were not added due to limited processing power. A feature that changed torpedo speed slightly with each shot was added and later removed after player feedback.
By April 1962, the group focused on showcasing the game, adding a time limit, hyperspace, and a second screen for spectators. Graetz presented a paper about the game at a computer users’ meeting in May 1962. The game became popular at MIT, with the PDP-1 lab banning play except during lunch and after work hours. Visitors, including writer Frederik Pohl, praised the game as a "lovely" experience that let players imagine being characters from science fiction stories.
Starting in mid-1962, members of the PDP-1 community, including Russell, spread the game to other schools and companies like Stanford University and DEC. This made Spacewar! one of the first video games available outside a research institute. Over the next decade, programmers at other institutions created variations, such as adding more players, cloaking devices, space mines, and first-person views. Some versions included Saunders’ gamepads. DEC used Spacewar! to test new PDP-1 systems and included it in a 1963 brochure. Though widely shared, the game remained limited by the technology of the time.
Distribution and legacy
Spacewar! became very popular among a small group of programmers in the 1960s. It was copied many times on other early computers before moving to smaller computers in the 1970s. The game was always free to use, and no one tried to sell it because there were not enough programmers to support a business. People shared the game by copying the code or by writing their own versions. Early versions were created at places like the PDP-1 computer at Bolt, Beranek, & Newman, a PDP-1 at Stanford University in 1963, and the University of Minnesota in 1967–68. At Stanford, the game was so popular that researchers created a special mode for playing it on a shared computer in 1966. In 1972, a famous computer scientist named Alan Kay said that Spacewar! could be found on any computer with a screen. Another person, Graetz, noted that the game was on nearly every research computer with a screen in the early 1970s.
Most of the game’s spread happened years after it was first created. Although some early versions existed near MIT and Stanford, it was not until after 1967 that computers with screens became common, allowing the game to reach more people. By 1971, it was estimated that over 1,000 computers had screens, compared to only a few dozen earlier. Many versions of the game were made for different computers, and in 1972, the game was so well known that Rolling Stone magazine sponsored a Spacewar! competition called the "Intergalactic Spacewar! Olympics." The event took place at Stanford University on October 19, 1972, using a version of the game that allowed five players to compete. This was the first video game tournament, and details about it were published in Rolling Stone in December 1972.
In the early 1970s, Spacewar! moved from large computers to commercial use, becoming the basis for the first two coin-operated video games. A student named Hugh Tuck at Stanford suggested making a version of the game that people could play for money. Although this idea was not possible at first because of the cost of computers, Tuck and Bill Pitts created a prototype called Galaxy Game in 1971 using a PDP-11 computer. Around the same time, Nolan Bushnell and Ted Dabney made another prototype called Computer Space, which became the first commercially sold arcade game. Although Tuck thought his version was better, many players believed both games were good versions of Spacewar!.
In 1977, Byte magazine published a version of Spacewar! that could run on early personal computers like the Altair 8800. In 1979, a version written in a simple programming language called Tiny BASIC was also created. More recent versions of the game have been made for modern computers and handheld devices. In 2012, a version of the original game was made available online using a computer simulation of the PDP-1. In 2022, a handheld console called the Analogue Pocket added support for playing Spacewar! using a simulated PDP-1. The only working PDP-1 computers today are at the Computer History Museum in California, where visitors can play Spacewar!.
Spacewar! also inspired many other games, such as Orbitwar (1974), Space Wars (1977), and Space War (1978). The 1979 game Asteroids used ideas from Spacewar!, including the "hyperspace" button and the shape of the player’s ship. Even a 1990 game called Star Control was influenced by Spacewar!. The game’s creator, Steve Russell, once said he was most proud of how many programmers it inspired to create their own games.
In 2007, The New York Times reported that Spacewar! was named one of the ten most important video games in history. The Library of Congress began preserving these games, and in 2018, Spacewar! was added to the World Video Game Hall of Fame. That same year, the Academy of Interactive Arts & Sciences honored the surviving creators of Spacewar! with the Pioneer Award for their contributions to the video game industry.