Spacewar
Encyclopedia : S : SP : SPA : Spacewar
- This article is about the PDP-1 game. To read about the arcade game, see Space Wars. To read about the Atari 2600 game, see Space War. To read about war in space, see interstellar war.
Gameplay
The basic gameplay of Spacewar involves two armed spaceships attempting to shoot one another while maneuvering in the gravity well of a star. The ships fired missiles which were unaffected by gravity (due to a lack of processing time). Each ship had a limited number of missiles and a limited supply of fuel. Each player controls a ship, and must attempt to simultaneously shoot at the other ship and avoid colliding with the star. Player controls included clockwise and counterclockwise rotation, thrust, fire, and hyperspace; using either the front-panel test switches with four switches for each player or optional control boxes.The hyperspace feature could be used as a last-ditch means to evade enemy missiles, but the reentry from hyperspace would occur at a random location and there was an increasing probability of the ship exploding with each use.
Options and features
Early versions of the game contained a randomly generated background starfield. However, the inaccuracy and lack of verisimilitude annoyed Samson, so he wrote a program based on real star charts that scrolled slowly: at any one time, 45% of the night sky was visible, every star down to the fifth magnitude. The program was called "Expensive Planetarium" (referring to the price of the PDP-1 computer), and was quickly incorporated into the main code.There were several optional features controlled by sense switches on the console:
- no sun (and thus no gravity)
- enable angular momentum
- disable background starfield
- the "Winds of Space"- a warping factor on trajectories that required the pilot to make careful adjustments every time they moved
A PDP-11-based GT40 Implementation at DEC
When the PDP-11-based GT40 vector graphics system was developed, Spacewar! was re-implemented to run on this system. As with the original version, gameplay was controlled by the front-panel toggle switches with four switches for each player controlling ship rotation left, ship rotation right, thrust, and weapons fire. It was quite common to see the paint worn off of the PDP-11 control panel above the eight switches used for Spacewar.
Because the missiles were launched with a velocity that was relative to the ship, a common ploy in this version of the game was to fire a missile while being whiplashed by a close approach to the sun. If the firing ship was pointing backwards along its orbital path, the fired missile had almost no absolute velocity and was simply left floating in space. If the opponent was not paying close attention, they would simply fly into such a lurking missile as they pursued and thereby be destroyed.
Spacewar today
As of May 2006, there is only known to be one working PDP-1 in existence, at the Computer History Museum in Mountain View, California. The computer and display were completely restored after two years of work, and Spacewar! is operational.A second PDP-1 belonging to the Computer History Museum is currently on tour as part of the Game On exhibition. However, this PDP-1 is not operational.
On May 15, 2006, the museum presented [The Mouse That Roared: A PDP-1 Celebration Event]. The PDP-1 was demonstrated running Spacewar! as well as other programs, and members of the public were able to play the game using makeshift controllers. Further PDP-1 demonstrations will be scheduled on a biweekly basis on Saturday afternoons.
Other games inspired by Spacewar
Over the years, many computer games have been inspired by Spacewar; some are known by the same name. Some are straightforward clones, but most have introduced additional variations to the game play, such as:
- various rates of acceleration
- various levels of gravity (even negative)
- missiles affected by gravity
- fuel (energy) regeneration over time
- shields
Home versions have appeared for most computer and console systems, with some becoming quite elaborate, introducing a wide variety of gameplay frameworks around the basic one-on-one combat system at their core.
Earlier computer and video games
The first graphical computer game is believed to have been OXO (a Tic-tac-toe game), developed by A.S. Douglas in 1952. William Higinbotham built Tennis for Two in 1958 using discrete analog hardware rather than a program for a digital computer.References
External links
- [History of Spacewar]
- [Dmoz directory for Spacewar]
- [Three vector-based Spacewar variants]
- [Playable Spacewar Java Applet]
- [1up.com's article naming Spacewar the most important video game ever made]
- ["Spacewar", a 1972 Rolling Stone article by Stewart Brand]
- [A 1972 Saga Magazine article about Spacewar]
- [Computer and Video Game History] describes Spacewar and earlier video games such as A.S. Douglas' Tic-Tac-Toe and William Higinbotham's Tennis for Two
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