Space Invaders and its many imitators fitted on one screen and needed a few controls at most. Defender gave the player a whole planet that scrolled past faster than they could follow, a radar strip showing everything they could not see, people on the ground to save, and five buttons as well as the stick. Electronic Games counted it among the few “truly original” coin-op games. It was the first video game by Eugene Jarvis, who had been programming pinball tables, and in Retro Gamer’s words it established Williams Electronics “as a major force in the videogames industry”.
Fast facts
- Maker: Williams Electronics.
- Design and program: Eugene Jarvis, with Sam Dicker, who made many of the explosions and effects, and Larry DeMar, who wrote the attract mode on the eve of the launch.
- Released: shown at the Amusement and Music Operators Association (AMOA) trade show, in the arcades in 1981.
- Hardware: a Motorola 6809 at 1 MHz driving a bitmapped display.
- Controls: an up-and-down joystick and five buttons: Thrust, Reverse, Fire, Smart Bomb and Hyperspace.
Built for a trade show
Jarvis had joined Atari’s pinball division in 1976 and moved to Williams, the Chicago pinball maker, as it began to look at video games. He pushed for a video project of his own and got it, with a deadline: the AMOA show, ten months away. Four months went on versions of Space Invaders and Asteroids that he decided were no good, though Asteroids’ thrust and hyperspace buttons survived. The idea that stuck came from the pinball designer Steve Ritchie. “Steve said: ‘Wouldn’t it be neat if you were flying over a planet on a screen,’” Jarvis told Joystik in 1982. “I eventually said: ‘We can’t do that yet, but what we can do is fly left and right.’” He described the aim more simply to Retro Gamer: “Everyone dreams about being able to fly, so we thought, ‘Let’s make a game where you really can.’” At first the ship flew only one way. The Reverse button came later.
The explosions were the trick. The 1 MHz hardware gave the game a bitmapped screen, and Sam Dicker used it to turn each pixel of a destroyed ship into its own flying fragment. Once the team started blowing things up, Jarvis said, “we knew we had something cool. Who’d remember Defender if it had tiny little explosions?”
The finish was close. In the last week the team patched the program by typing hexadecimal directly into memory, because a proper rebuild took 45 minutes, and a power cut would have lost the lot. At 10pm on the night before the show, Jarvis recalled, Larry DeMar walked in and asked whether the game would have an attract mode, the demonstration that plays when nobody is at the machine; DeMar wrote one on the spot. The game was ready at 4am. The first set of chips they burned did not work at the show, and the second did.
How it plays
The player’s ship flies over a planet far wider than the screen. Above the main view sits the Scanner, a strip showing the whole planet at once: the terrain, the humanoids standing on it and every alien, each in its own colour. You spend the game glancing between the two.
The left hand works the joystick, which moves the ship up and down, and the Reverse button, which flips it to face the other way. The right hand works Thrust, Fire and Smart Bomb. Videogaming Illustrated complained in 1982 that the fifth button, Hyperspace, was “oddly misplaced” and “completely out of reach”; it jumps the ship to a random spot, and good players rarely used it. Each 10,000 points brought an extra ship and an extra smart bomb, which destroys every alien on the main screen.
The aliens each do one job:
| Alien | What it does |
|---|---|
| Lander | Drops from the sky, snatches a humanoid and carries it upwards |
| Mutant | A Lander that reaches the top with its captive; it chases the ship |
| Bomber | Drifts and leaves a trail of mines |
| Pod | Harmless until shot, then bursts into Swarmers |
| Swarmer | Small, fast and firing |
| Baiter | Arrives if a wave takes too long, and flies faster than the ship |
Shooting a Lander that is carrying someone drops the humanoid; catching it in mid-air and setting it down on the ground is worth 1,150 points in all. Lose every humanoid and the planet explodes, leaving the ship alone in space with the surviving aliens, every Lander now a Mutant. A fresh set of humanoids arrives every fifth wave.
Reception and sales
Joystik called Defender “the biggest success of 1981”. Electronic Games gave it an honourable mention in its arcade awards and said it was “one of the most popular—and most challenging—contests to reach the family amusement centers in many years”. It was also a game people competed on: a Defender score of tens of millions at the Twin Galaxies arcade became a record nobody could check. In Britain, Julian Rignall wrote a Defender guide for Personal Computer Games.
Jarvis thought its difficulty was fair because it forgave a bad start. “Games like Defender, Robotron and Asteroids give an extra ship every 10,000, 25,000, or what have you,” he said. “You never feel like you’re out of the game.”
Home versions and imitators
Atari’s cartridge for the VCS (the Atari 2600) came out in 1982. Video Games Player put it third among the biggest home hits of that year, at 3.5 million cartridges, behind Pac-Man and Donkey Kong. Atari also made versions for its 5200 console and its 400 and 800 computers, and in late 1983 its new Atarisoft label announced Defender for other companies’ machines: the ColecoVision and Intellivision consoles, and the IBM PC, Apple II, Commodore 64, VIC-20 and TI-99/4A computers.
Other programmers wrote their own. Quicksilva sold a Defender for the ZX81; Jez San’s first commercial game, Skyline Attack for the Commodore 64, was in his words “a Defender clone with nice graphics”; and on the Amiga, Mark Sibly demonstrated his Blitz BASIC with a Defender conversion.
Stargate and after
Williams wanted a sequel in four months. By then Jarvis and DeMar had left to form their own company, Vid Kidz, and they wrote Stargate under contract, working in shifts on the expensive Motorola development system. Jarvis thought it “the better game”; Williams later renamed it Defender II after a trademark dispute. Vid Kidz went on to make Robotron: 2084, which kept Defender’s rescue of humans but put it on a single crowded screen.
Released source code
The 6809 assembly-language source of Defender was published on GitHub by the historicalsource archive in January 2021, with no licence stated. Other enthusiasts have since used it to rebuild the original arcade ROMs.
Sources
- Joystik, vol. 1 no. 1, September 1982, “Innerview: Eugene Jarvis”, by Wayne Robert Williams: Steve Ritchie’s idea, “fly left and right”, “the biggest success of 1981”, the extra ship every 10,000 points.
- Retro Gamer, issue 24, 2006, pp. 78–80, “Desert Island Disks: Eugene Jarvis”: Atari’s pinball division, Williams, the AMOA deadline, the discarded Space Invaders and Asteroids reworkings, the flying idea, Sam Dicker’s explosions and the 1 MHz hardware, patching in hex, Larry DeMar’s attract mode, the chips that failed, Stargate and Defender II, Vid Kidz.
- Videogaming Illustrated, August 1982, pp. 45 and 56–58: the six controls and the misplaced Hyperspace button, the smart bombs and extra ships, the Scanner, the aliens, the points for rescues, the exploding planet and the fifth-wave humanoids.
- Electronic Games, vol. 1 no. 2, March 1982, p. 49: Arcade Awards, honourable mention, “truly original coin-op games can be counted on the fingers of one hand”.
- Electronic Games, vol. 1 no. 6, August 1982, p. 66, Bill Heineman, “Save the Survivors in Defender”: “one of the most popular—and most challenging—contests”, the list of aliens.
- Video Games Player, vol. 2 no. 1, September 1983, p. 12: “Biggest 1982 hits”, Defender third at 3.5 million cartridges.
- Electronic Fun with Computer & Games, vol. 2 no. 2, December 1983, p. 104: the “initial Atarisoft multiple-format release list”, with Defender for ColecoVision, Intellivision, IBM PC, Apple, C-64, VIC and TI-99.
- “Defender (1981 video game)”, Wikipedia (web, secondary): the Atari 5200 and 8-bit computer versions. https://en.wikipedia.org/wiki/Defender_(1981_video_game)
- “historicalsource/defender”, GitHub, January 2021 (web, secondary): the published source code. https://github.com/historicalsource/defender