Asteroids | Code Like It's 198x

Asteroids gave the player five buttons, a small triangular ship and a screen full of rocks that broke into smaller rocks when shot. Ed Logg’s game for Atari arrived in the arcades in November 1979 and became the company’s best-selling coin-op: more than 70,000 machines, according to Video Games in 1982. Its pictures were not built from dots like a television’s. A vector monitor drew them as bright, thin lines, so the ship could turn to any angle and a rock could drift in from any edge. The game also left a gap in its rules that expert players found, and some of them used it to play for whole weekends on a single coin.

Fast facts

Maker: Atari, coin-op division.
Programmer: Ed Logg, from an idea by Lyle Rains; hardware and sound by Howard Delman.
Released: November 1979. Video Games gave the date as 6 November; Electronic Games said Atari’s plant at Tipperary, Ireland, had shipped the first machines in October.
Sales: more than 70,000 machines.
Hardware: a 6502 processor and a vector generator driving a black-and-white XY monitor, which Atari called QuadraScan.
Controls: rotate left, rotate right, thrust, fire and hyperspace.
Home versions: Atari 2600, Atari 400/800 and Atari 7800.

A game nobody wanted to play

The idea began with a game that did not work. Atari’s engineers had spent a long time on a two-player space game called Cosmos, earlier Planet Grab, in which players claimed planets. It “really wasn’t fun,” Howard Delman told Retro Gamer, until “someone made it so you could blow up the other guy’s planets. And suddenly it was fun.” Logg remembered a version with an asteroid in the middle that could not be destroyed; players kept shooting at it anyway. Lyle Rains, vice-president of engineering in the coin-op division, drew the lesson. “He said everyone just seems to shoot the rock,” Logg recalled, “so let’s create a game that lets you blow it up.”

Rains wanted to build it on an ordinary raster screen. Logg argued for vectors. “The higher resolution meant you had more control of where you were aiming, not just this blob,” he said, and he knew the hardware from Lunar Lander, Atari’s first vector game, whose on-screen lettering he had worked on. Logg remembered the meeting with Rains as taking place in April 1979. The program’s own header is dated earlier: “DATE INITIATED: 23-FEB-79”, with “PROGRAMMER: ED LOGG” underneath.

Logg started on a modified Lunar Lander board, “this little four-by-four inch board with five buttons and wires coming off it”, and got the ship flying first. There was no design document. He tried a ship with no friction and one with no inertia before settling between them, and sketched rock shapes on paper. Some effects came free with the monitor: the vapour trails behind moving objects were the phosphor still glowing where the beam had been.

How the pictures were drawn

A television builds its picture from lines scanned across the whole screen, top to bottom. A vector display moves its electron beam only where something needs drawing. The Home Computer Course explained it for British readers in the mid-1980s: “if a square is needed the beam describes a square shape,” and making it bigger or smaller “is simply a case of applying a larger or smaller voltage to the deflection coils”. Every line on an Asteroids screen is equally bright, and nothing is solid; in Electronic Games’ comparison, it was the difference between a connect-the-dots puzzle and the smooth lines of an Etch-a-Sketch.

The display grew out of a prototype that Atari’s research group at Grass Valley showed the coin-op engineers in early 1978. Delman, working with Rick Moncrief, turned it into something games could be built on. Atari sold the result under the trademark QuadraScan. Asked by a reader in 1982 how it differed from Cinematronics’ Vectorbeam system, Electronic Games answered that there was “no real difference” in principle; the name belonged to Atari.

The program listing, published in 2021, shows how the work was divided. The 6502 does not draw lines itself. It writes a list of drawing instructions (each a position, length, scale or brightness) into 2K of vector RAM, and a separate circuit, the vector generator, reads the list and steers the beam. The shapes of the ship, rocks and saucers sit ready-made in 2K of vector ROM, next to 6K of program ROM. There are two lists: once per frame the main loop waits for the beam to halt, switches the vector generator to the list it has just built, and starts it drawing while the program fills the other. Later writers call this circuit the Digital Vector Generator, and Atari went on to use it in Asteroids Deluxe.

The display could be damaged, too. “If the game crashed, the beam would go to the middle of the screen and if you left it on, it would burn a hole in the phosphor,” Logg told Retro Gamer. Atari added a “spot killer” that shut the display down when the beam was not moving enough. Nobody told Logg how much movement it needed, so he put the score at the top of the screen and the Atari copyright line at the bottom to keep the beam busy. On some machines, with one rock and one ship left, the screen still faded out.

Rocks, saucers and a heartbeat

The listing gives the scores: 20 points for a large rock, 50 for a medium one and 100 for a small one, 200 for the large saucer and 1,000 for the small one, with an extra ship every 10,000 points. Rocks the saucer shoots score nothing. Logg wanted two saucers from the start. The large one fired at random “like cannon fodder to get you used to the concept”; the small one, which the program sends in more often as the score rises, “was about making you move. Run away, you’re going to die if you stick around!” A timer that grew shorter as the game went on kept the saucers coming, so a player who stopped shooting rocks got no rest.

Hyperspace moved the ship somewhere random, and the program sometimes blew it up on re-entry. Logg later said he would rather have used a shield. The low throb under the action was Delman’s. “I was really trying to do a heartbeat,” he said: as the thumps sped up he wanted players to feel their own pulse speeding with them. There was no sound chip. Delman built a circuit for each of the game’s 13 sounds by hand and wired them onto Logg’s board. The game’s messages could be switched between English, German, French and Spanish.

Asteroids kept a table of the ten best scores with three initials each. Logg said he took the idea from Exidy’s Star Fire. Without battery backup, the table only lasted until the machine was switched off.

Atari ran two focus groups in June 1979, one of older players who knew Spacewar! and one of teenagers who played Space Invaders, and watched them through one-way glass. The first field test was at an arcade in Old Sacramento that summer. “A guy walks over and puts in his quarter,” Logg recalled, “and he died three times in about 20 seconds. Then he reached out and put another quarter in.” Asteroids went into production so quickly that Atari stopped building Lunar Lander at about 5,000 machines to make room on the line. Delman said around 200 Asteroids boards went out in Lunar Lander cabinets.

Lurking

The small saucer originally fired as soon as it appeared. “If you were right next to him he’d nail you,” Logg said. “People said it wasn’t fair, so I said okay, I’ll give you a second before he takes his shot so you can see where he’s at. Unfortunately that opened the big fat window to lurking.” A lurking player shot every rock but one, then waited for saucers and picked them off at 1,000 points each, piling up spare ships along the way. Logg had tried the tactic himself, failed, and assumed nobody else could manage it.

Players managed it. Electronic Games reported in 1981 that Greg Davies of Fresno had scored 15,449,950 on one quarter. “Whenever I wanted to take a drink or go to the bathroom,” he said, “I piled up a bunch of bonus ships.” David Jeanise raised the record to 22,254,110 on 14 June 1981. Operators complained about machines tied up for 30 hours at a time, and other manufacturers sold kits to change the program. Atari made a new chip to stop lurking, but, Logg said, “a lot of operators found that with it their earnings went down and wanted it put back to the old way.” Atari’s own record list in 1983 put Scott Safran at the top with 41,336,440 points in a game of 53 hours and 8 minutes at Newtown, Pennsylvania; Retro Gamer dated the game to November 1982, when Safran was 15. Twin Galaxies later recognised the score as the record.

Big scores also exposed a bug. Earn enough spare ships and the game slowed down, because it drew every one of them in a row across the screen. “I should have limited the number of the player spaceships to ten or something,” Logg told Edge.

A hit in the arcades

Electronic Games reported that Asteroids led all coin-op games in takings in 1980 and was “already starting its third successful year” at the end of 1981. At Atari’s 1980 Space Invaders championship, one of the prizes was a cocktail-table Asteroids, and it drew so much attention that the magazine saw it as the heir to the older game (see the origins of esports). Looking back in 2010, Tristan Donovan put it second only to Space Invaders among the arcade games of 1979. Edge in 2002 gave the game’s earnings as $150 million for Atari and more than $500 million for the operators who ran the machines. Logg suspected there were more Asteroids in the world than Atari made: “I’ve certainly seen counterfeit boards.”

Asteroids Deluxe

Asteroids Deluxe followed in March 1981. It swapped hyperspace for a shield that could only be used briefly, and added killer satellites and “smart” saucers. The monitor lay on its side and reflected its picture in a tilted, half-silvered mirror. “The game originally tested as being too difficult,” Atari’s Frank Ballouz told Electronic Games, and Atari toned it down. Logg had no part in it: Dave Shepperd took Logg’s code and extended it, while Logg was busy as a supervisor. Rains lists Asteroids Deluxe among his own credits. Owen Rubin’s two-player Space Duel and Ed Rotberg’s Blasteroids came later. Blasteroids went to Mirrorsoft in the deal that passed the console rights to Tetris to Atari Games.

At home

Atari brought Asteroids to its own machines. For the 2600, Brad Stewart took on the conversion as a challenge, while Rob Fulop did Missile Command; ANALOG listed the cartridge among Atari’s new VCS games for early 1981. Its game variations let the player escape by hyperspace, by raising shields or by flipping the ship round 180 degrees. It needed 8K of ROM, twice what the console could see at once, and Electronic Games explained that it used “a special bank switch that flip-flops two 4K programs” (see bank switching). The Atari 400 and 800 got a cartridge version in the first half of 1981, which ANALOG said added colour and play for up to four people.

The Atari 8-bit and 2600 versions drew with dots, not lines. So did the Atari 7800 version, one of the games announced with that console in 1984. When ANALOG’s Bill Kunkel reviewed it in 1988, he found shaded rocks that could be seen spinning, “almost glittering graphics”, two-player games and four difficulty levels: “If you’re one of the millions who always enjoyed Asteroids … this 7800 program will knock you out.”

Logg was not consulted on any of them. “I played ’em,” he told Retro Gamer, and thought “they just didn’t obey any of the rules.”

Legacy

Vector games came in numbers after Asteroids, from Atari’s Battlezone and Tempest to GCE’s home Vectrex, whose built-in game Mine Storm borrowed the rock-splitting idea. Eugene Jarvis tried and abandoned an Asteroids variant before writing Defender, and kept its thrust and hyperspace buttons. The vector graphics entry explains the technique more generally.

The original assembly-language source for Asteroids, Asteroids Deluxe, the cocktail version and the Atari 7800 version is public: the historicalsource archive on GitHub published it, the 7800 version in 2019 and the arcade versions in October 2021, with no licence stated.

Sources

Video Games, vol. 1 no. 3, December 1982, Steve Bloom, “The incredible, incredible story of Atari”, p. 48: release on 6 November 1979, 70,000 units, Cosmos and Planet Grab, the credits for Logg, Delman and Rains, Lunar Lander stopped at 5,000 units, 200 Asteroids in Lunar Lander cabinets.
Electronic Games, vol. 1 no. 1, December 1981, pp. 32–33: the Space Invaders championship prize, the five buttons, Quadrascan, the Tipperary plant and 70,000 units, the lead in 1980 takings, the third year, Greg Davies’s and David Jeanise’s scores, modification kits, Asteroids Deluxe and Frank Ballouz.
Electronic Games, vol. 1 no. 2, March 1982, p. 53: Quadrascan and Vectorbeam compared.
Electronic Games, November 1982, p. 102: the 2600’s 8K bank switch in Asteroids and Missile Command, as set out in the bank switching entry.
Electronic Games, vol. 2 no. 14, September 1984, pp. 28–29: the Atari 7800 and its first games, Asteroids among them.
ANALOG Computing, issue 1, January/February 1981, pp. 3 and 25: Asteroids on cartridge for the Atari 400 and 800 in the first half of 1981; the VCS Asteroids and its options.
ANALOG Computing, issue 59, April 1988, pp. 74–75: Bill Kunkel’s review of the Atari 7800 version.
Electronic Fun with Computers & Games, vol. 1 no. 10, August 1983, p. 79: Rob Fulop on Brad Stewart and the 2600 Asteroids.
Atari Age, vol. 2 no. 3, September 1983, p. 32: “Official Atari Coin Video Records”, Scott Safran, 41,336,440 in 53 hours 8 minutes, Newtown, PA.
The Home Computer Course, part 9 (Orbis), “Seen in Perspective”: how a vector display draws.
Edge issue 117, December 2002, pp. 106–109, “The making of… Asteroids”: Rains and the indestructible asteroid, the XY monitor, the 6502, 70,000 units and the $150 million and $500 million estimates, the lurking change and the lurk-limiting EPROM, the slowdown with too many ships.
Tristan Donovan, extract from Replay: The History of Video Games, Edge issue 217, August 2010, pp. 83–84: the Grass Valley prototype, Delman and Rick Moncrief, Lunar Lander, the heartbeat, Asteroids second to Space Invaders in 1979.
Paul Drury, “The making of Asteroids”, reprinted in The Atari Book (Retro Gamer, 2012), pp. 134–139: the field test, Cosmos and Planet Grab, raster against vector, the Lunar Lander board, the saucers and the timer, hyperspace and the shield, the focus groups, Delman’s 13 sounds, the spot killer and the copyright line, lurking and the anti-lurking chip, Star Fire, Asteroids Deluxe, Space Duel and Blasteroids, counterfeit boards.
Paul Drury, “Desert Island Disks: Ed Logg”, Retro Gamer issue 29, 2006, pp. 76–78: the spot killer, the lurking change, the high score table without battery backup, the home versions.
Paul Drury, “Asteroids” high score feature, Retro Gamer issue 28, 2006, pp. 104–105: Scott Safran’s game in November 1982 and Twin Galaxies.
Retro Gamer issue 24, 2006, pp. 78–80, “Desert Island Disks: Eugene Jarvis”: Jarvis’s Asteroids variant, as set out in the Defender entry.
Asteroids program listing (Atari, 1979; the file ASTROD and its includes), historicalsource/asteroids on GitHub, October 2021: header date and programmer, memory map (vector RAM, vector ROM, program ROM), the double-buffered vector lists, scoring, the extra ship every 10,000 points, hyperspace re-entry, the ten-entry high score table and the four languages. https://github.com/historicalsource/asteroids ; the other versions at https://github.com/historicalsource/asteroids-deluxe , https://github.com/historicalsource/asteroids-cocktail and https://github.com/historicalsource/asteroids-7800
“Asteroids Disassembly”, 6502disassembly.com (web, secondary): the name Digital Vector Generator and its use in Asteroids Deluxe. https://6502disassembly.com/va-asteroids/