Asteroids was Atari's response to Taito Corporations's Space Invaders, and became their all-time best-selling game. Atari would sell somewhere in the order of seventy-thousand arcade game machines, generating approximately one hundred and fifty million dollars in revenue, while the machines themselves made hundreds of millions of dollars for operators.
Atari's original vision was for a game called Cosmos, which was virtually a clone of the Space Wars game released by Cinamatronics in 1978 (which was itself based on Spacewar!), with a few asteroids added for effect. Atari engineer Lyle Rains, who was developing the concept for the game, hit on the idea of giving the asteroids a more prominent role. The player would be required to pilot their spaceship through the asteroid field, without colliding with any of the asteroids. The spaceship itself was armed with a weapon, and points would be awarded for destroying as many asteroids as possible.
Rains asked Atari game designer and programmer Ed Logg for his input. Logg liked the basic concept but thought the game still needed to feature alien spacecraft. Logg had played both Spacewar! and the coin-operated Galaxy Game (which was based on Spacewar!) while a student at Stanford University, and was keen to ensure that both the spacecraft and the asteroids themselves should behave in accordance with the laws of physics.
In order to achieve this, Logg realised that he would need a relatively high display resolution. The resolution of available raster (bitmapped) graphics hardware was simply not high enough for what he had in mind, so he insisted on the use of a vector graphics display. Atari had already invested a significant amount of time and effort into developing vector graphics hardware, and had used it in their implementation of the Lunar Lander arcade game.
The Lunar Lander game would never achieve either the widespread popularity or financial success of other titles released during the same period (although I distinctly remember playing this game in an arcade on more than one occasion) but it ably demonstrated the capabilities of Atari's digital vector generator (DVG). Atari engineer Howard Delman, who had refined the prototype hardware for Lunar Lander, was asked to produce a suitably modified version of the DVG hardware for Asteroids.
Delman would also design the circuitry used to generate Asteroids' digital soundtrack. Rains turned over the design and programming of Asteroids to Logg, who was assisted in this task by fellow Atari employee Dominic Walsh. Logg knew the game would be a smash hit when, during the development process, Atari employees had to be prised away from a version of the game running on a prototype arcade machine so that development work on the game could continue.
Initial demand for the game was so great that Atari ceased production of the Lunar Lander arcade machines in order to meet the demand for Asteroids. In fact, the first two hundred or so units shipped were apparently built using cabinets originally intended for Lunar Lander. Once installed in arcades, Asteroids was so popular that arcade operators reportedly had to increase the size of the box used to collect the coins inserted by players.
Opinions vary on whether Asteroids replaced Space Invaders as the most popular and financially successful arcade game of its time. In fact, the two games often appeared side-by-side in arcades, and both were enormously successful. Both were relatively simple in terms of gameplay, both were addictive, and both featured an electronic soundtrack that increased in tempo as the speed of the game increased.
Arguably, a large number of people (myself included) found both games equally enjoyable, though perhaps in different ways. Asteroids probably provided more variety in terms of the challenges faced by players, as well as more scope for developing strategies in order to achieve a high score.
The game itself places the player in command of a spaceship with a forward-firing weapon, initially at the centre of the screen. The player can use thrusters to maneuver the ship and has an unlimited supply of ammunition. The major threat comes in the form of several large asteroids that move randomly across the screen in different directions. If the spaceship collides with one of these objects, it is destroyed. When it has been destroyed three times, the game is over.
The player can fire their weapon at the asteroids to destroy them, but an initial hit will only succeed in breaking the asteroid into two smaller asteroids, each of which moves faster than the original, and each of which can potentially destroy the spacecraft. Shooting either of these smaller pieces produces two even smaller asteroids that move even faster. Once you shoot these smallest asteroids, however, they will be totally destroyed and no longer pose a threat.
As if things were not difficult enough, a further threat is provided in the form of flying saucers that appear at random time intervals, move horizontally (and sometimes diagonally) across the screen, and try to destroy the spaceship (either by firing their weapons at it or by colliding with it). There are two different types of saucer. The larger of the two is the least dangerous by virtue of the fact that it fires seemingly at random, and presents a larger target. The smaller saucer is more dangerous, because it moves faster and appears to be able to target the player's spaceship far more accurately.
The playing field is levelled a little by the fact that the flying saucers are also destroyed if they collide with an asteroid. One interesting feature of the game is the hyperspace option, undoubtedly copied from Spacewar!, which allows a player to get out of a tight spot by making a hyperspace jump. This manoeuver is only meant to be used as a last resort, as it carries with it the risk of reappearing in the path of an asteroid or an enemy projectile (or even occasionally self-destructing).
Shooting a large asteroid generates twenty points. Successively smaller asteroids are worth more points, with the smallest being worth one hundred points. Destroying the larger of the two types of flying saucer is worth two hundred points. The greatest number of points is achieved by destroying the smaller saucer, which will gain the player one thousand points.
Perhaps due to a certain lack of foresight on the part of the game designers, the maximum number of points that can be achieved is just short of one hundred thousand points, at which point the score reverts to zero (many players quickly developed sufficient skill to achieve the maximum score). Once all of the asteroid fragments and any remaining saucers have been destroyed, the game starts again with a larger number of slow moving asteroids (up to a maximum of twelve). As the player's score increases, the speed and targeting accuracy of the smaller flying saucer also increases.
The game has a "wrap-around" feature that allows a moving object to disappear off the edge of the screen and reappear at the corresponding point on the opposite edge, moving with the same velocity (i.e. in the same direction and at the same speed). This applies to asteroids, spacecraft, flying saucers and weapon projectiles. On achieving a sufficiently high score, a player can add their score to the high scores listing, together with their initials.
Seasoned Asteroids players developed a number of high scoring strategies, some of which involved exploiting "bugs" in the game's program. One such strategy used a bug in the earliest version of the game that allowed the player to hide their spaceship in the area occupied by the score and pick off targets prom a position of relative safety. Needless to say, these glitches were addressed in later versions of the game, since they allowed a sufficiently skilled player to play the game indefinitely without parting with any more money.
The arcade version of the game came in various forms, the most popular being the upright cabinet and the cocktail table version. Players control the spacecraft using five buttons. Two buttons are used to rotate the spacecraft (left or right), one button fires the main thruster, another button fires the spacecraft's weapon, and the last button is used to initiate a hyperspace jump.
The electronics hardware includes a MOS Technology 6502 8-bit microprocessor that executes the game's program code. The digital vector generator (DVG) developed by Atari themselves receives graphics commands from the 6502 microprocessor and sends the appropriate signals to the high-resolution monochrome vector graphics CRT monitor in order to draw the screen display.
The game's audio tones are generated by a number of dedicated circuits, each of which is activated by the microprocessor writing to a different address in memory. Each of the buttons used by the player to control the game is mapped directly to a specific location in the microprocessor's address space.
The game code itself requires just six kilobytes of read-only memory (ROM), with a further two kilobytes of ROM required for the vector data for the various onscreen objects and text. Even so, porting the game to the Atari 2600 home console presented a challenge to Atari engineer Brad Stewart (to whom the task was assigned), since the Atari 2600 could only address four kilobytes of memory. Stewart came up with a fairly ingenious bank-switching scheme to get around this limitation, which involved the processor switching backwards and forwards between two separate four-kilobyte memory banks.
The game was subsequently adapted for a number of home game consoles, both Atari's own and those of other console manufacturers, under license. The console versions were programmed using raster graphics rather than vector graphics, but managed to retain the appeal of the original version. Versions of the game also appeared on Atari's 8-bit home computers, and versions would later appear for a number of other personal computers including the IBM PC.
Asteroids inevitably spawned a number of sequels, the first of which was Asteroids Deluxe, released in 1980. New features included a shield that replaced the original hyperspace feature, rotating asteroids, a new kind of alien flying saucer, and a redesigned cabinet intended to give the display a more three-dimensional appearance. Later sequels from Atari include Space Duel in 1982 and Blasteroids in 1987.
It is a tribute to the success of Asteroids that it has been often imitated, spawned many clones, and been ported to just about every platform possible. The game survives to this day in innumerable formats, including versions for the PC, home game consoles, mobile devices, and countless web-based simulations. If you have never played this game before, and want to experience for yourself just how addictive it can be, you can try one of the online versions referenced above, or play the online version on Atari's official website here.
This article was first published on the TechnologyUK.net website in January 2009.