A Robotron wave starts with the player in the middle of a black screen and everything else coming for them. Grunts march in from all sides, indestructible Hulks lumber about, Brains hunt down the stray humans and reprogram them, and somewhere in the crowd Mommy, Daddy and Mikey, the last human family, wander about waiting to be saved. The player holds two joysticks: the left moves the hero, the right fires in any of eight directions, whichever way they happen to be running. Electronic Games thought it “perhaps the fastest-moving arcade game ever created” when it reached arcades in 1982. Its designer, Eugene Jarvis, put it more simply: “You cannot play a casual game of Robotron. It demands your everything.”
Fast facts
- Designers: Eugene Jarvis and Larry DeMar, at their company Vid Kidz.
- Manufacturer: Williams Electronics, which built and sold it.
- Arcade release: 1982. The pair’s third Williams game, after Defender and Stargate.
- Controls: two eight-way joysticks, one to move and one to fire.
- Hardware: Williams’s 6809-based board with a new graphics chip, the blitter, to move the images.
- Home versions: Atari 5200, Atari 400/800 and Atarisoft versions for other computers (1983–84), Atari 7800.
- Successors: Smash TV (1990) and Total Carnage (1993), and the modern twin-stick shooters from Geometry Wars on.
Space Invaders in two dimensions
After Defender and Stargate, both of which scrolled across a planet, Jarvis wanted the opposite: a single screen with no way out. “From a game design perspective, the set-up was to essentially take Space Invaders into two dimensions,” he told Retro Gamer. “Instead of moving in a line fighting enemies coming from above, Robotron allowed you to move in full 2D space, with enemies coming from all sides and shooting in all directions at once.” Where Defender had been about the freedom to fly around a whole world, he said, Robotron “was all about the tension of confinement. There was no escape from the confrontation, no fight or flight, only fight or fight.”
He took ideas from Stern’s Berzerk, a robot-shooting game he loved, and from Chase, an early game for the Commodore PET in which the player lured pursuers into a minefield. His first version worked like Chase: one joystick, and the player tricked the robots into running into electrodes. It was fun “for about five seconds”, he recalled. The human family came from Defender, whose astronauts the player had to protect: “a game has to be about more than just killing,” Jarvis said.
The second joystick
Berzerk had frustrated him. “I loved Berzerk but it was very frustrating having to move towards an enemy you wanted to shoot, especially as holding the fire button down meant your player remained stationary,” Jarvis said. A car accident after Stargate had shattered his right hand and made the game almost impossible for him to play. The answer was to move with one joystick and fire with another. He wired a second Atari 2600 joystick to the prototype’s control panel, and “knew I was on the right track”.
Jarvis remembered it as “such a basic idea that it was amazing it hadn’t been done before”. Retro Gamer was more careful in 2012: Robotron “wasn’t the first videogame to use it, but it was arguably the first shooter that needed dual-stick controls as a conscious design choice.” The twin sticks made it easier to pick up than Defender, with its five buttons, but the game still demanded that each hand do something different. Early versions were harder still. “Robotron actually went out even harder at first, but it was just too brutal,” Jarvis said. “We had to lighten up the game.”
Jarvis also noticed who played it. From cigarette burns on the control panels he reckoned the players were about half right-handed and half left-handed, far more left-handers than in the population. His theory was that left-handers, used to a right-handed world, made better Robotron players.
Six months, 150 robots
The core of the game was running within three days, and the whole took six months. The pair started from their Defender and Stargate program. “I concentrated on the character/projectile behaviour, level design and game mechanic, while Larry basically did everything else, including all the mind-blowing special effects,” Jarvis said.
The hard part was the numbers. Williams’s hardware drew on a bitmapped screen, and moving that many images was too much for the main processor alone. Jarvis and DeMar specified what they called the “Robotron graphics DMA chip”, a blitter that copied images of any size into the screen memory, and Williams used it in the games that followed. With a 1 MHz graphics processor and “very clever machine code and micro code”, Jarvis said, the game could handle about 150 enemies at once: “Larry and I nearly lost our minds making it work.” All the sound came from one channel, shared out by priority so that the most important effect always won. “No-one ever noticed,” Jarvis said.
He also made the robots unpredictable. “Virtually no behaviour in Robotron is deterministic,” he said. “There’s always a random factor added to any behaviour for more interest. It’s amazing how players will associate random events with mood or intelligence of enemies.”
The robots and the family
Each kind of robot behaved differently:
| Enemy | What it does |
|---|---|
| Grunts | Walk straight at the player and try to overwhelm them by numbers; they do not shoot |
| Hulks | Cannot be destroyed, and shots only slow them; they kill any humans they reach |
| Brains | From wave 5; fire cruise missiles that follow the player, and turn humans into Progs |
| Progs | Reprogrammed humans who race at the player |
| Spheroids | Release Enforcers, which pursue the player and fire guided missiles |
| Quarks | Release Tanks, which fire bombs or try to run the player down |
| Electrodes | Fixed hazards that robots can be lured into |
Rescuing the family was where the points were. The first human collected in a wave was worth 1,000 points, the next 2,000, then 3,000, 4,000 and 5,000 for each one after, until the player died or the wave ended. Atari’s Steve Woita, who played it in the arcade at the back of Atari’s building, called the scoring “brilliant”: “It was just magic.” Every rescue was a gamble, and Jarvis wanted it that way. “At each millisecond the player must recalculate an optimal strategy,” he said, “evaluating the risk of dying versus the point gain of rescuing humans versus the value of killing off the enemy versus the value of fleeing.”
Home versions
Two joysticks were a problem at home, where consoles and computers had one each. Atari’s version for its 5200 console came with a holder for two 5200 controllers, so that players could use one to move and the other to fire, as in the arcade. Electronic Games called the Atari 400/800 version “a virtually flawless arcade-to-home translation” in 1984: two joysticks plugged in gave the arcade controls, and less experienced players could use one. Atari’s Atarisoft label also sold Robotron for other companies’ computers. The Apple II version worked differently, and Electronic Games found it “distantly recognizable” at best, though entertaining. A version for the Atari 7800 was shown in 1984 with more than 70 robots on screen at once, and was on sale in Britain by 1987.
Jarvis blamed the hardware for how few twin-stick games followed: “The ubiquitous single-stick paradigm effectively locked the twin-stick genre out of the consumer space. Most of the ports suffered from lack of dual joysticks, hardware performance, or if there were two joysticks, how do you nail them down to the coffee table?” Other programmers borrowed the idea anyway. Paul Holmes’s Wild West Hero on the Spectrum swapped the robots for cowboys, and Jeff Minter’s shareware Llamatron came out for the Atari ST and Amiga.
Twin sticks again
“When Robotron came out, I felt that the twin-stick control would rapidly dominate the industry,” Jarvis said. “But surprisingly few titles came out.” Vid Kidz’s next game, Blaster, dropped the second stick. Atari’s Black Widow borrowed the controls: its designer, Bruce Merritt, remembered Atari’s engineers having a Robotron machine in their common area and “calluses from wrenching the joysticks”.
Jarvis came back to the idea at Williams with Smash TV in 1990 and Total Carnage in 1993. The real return came when console controllers gained two analogue sticks. “It wasn’t until the dominance of FPS games drove dual-stick adoption in the Xbox and PlayStation DualShock controllers that the twin-stick approach became standard, almost 20 years after Robotron,” he said. Stephen Cakebread’s Geometry Wars began as a hidden extra in Bizarre Creations’ Project Gotham Racing 2, written one evening when he had code reading both of the Xbox pad’s sticks. He took a lesson from Robotron too: with only eight directions to fire in, where the player stood mattered, and he worked that kind of decision into the later Geometry Wars games.
Released source code
The 6809 assembly-language source of Robotron: 2084 was published on GitHub by the historicalsource archive in January 2021, alongside Defender’s, with no licence stated.
Sources
- Retro Gamer: The Ultimate Retro Companion, vol. 2 (Imagine, undated), pp. 42–45, “The Making of Robotron: 2084”: release details, Space Invaders “into two dimensions”, three days and six months, the 1 MHz graphics processor and 150 enemies, the random behaviour, the enemies and the family, the single sound channel, Berzerk and the car accident, “such a basic idea”, “it demands your everything”, Jarvis on strategy.
- Retro Gamer issue 107, October 2012, pp. 24–29, Mike Bevan, “30 Years of Robotron”: the influences (Berzerk, Chase, Defender), the one-stick prototype and the second joystick, the division of work with DeMar, the “Robotron graphics DMA chip”, “fight or fight”, the family and Defender’s astronauts, “wasn’t the first videogame to use it”, the harder first version, the left-handers, Steve Woita on the scoring, Jarvis on single-stick consoles and on the twin-stick revival, Blaster, Black Widow and Bruce Merritt, Wild West Hero, Llamatron, Smash TV, Total Carnage, Stephen Cakebread on Geometry Wars.
- Electronic Games vol. 1 no. 6, August 1982, pp. 51–53: Robotron in the arcades, “the third entry” after Defender and Stargate, the two joysticks, “perhaps the fastest-moving arcade game ever created”.
- Atari Age vol. 2 no. 4, November–December 1983, p. 36: the Atari 5200 cartridge and its controller holder.
- Electronic Games vol. 2 no. 10, December 1983, p. 27: Atarisoft advertisement listing Robotron: 2084.
- Electronic Games vol. 2 no. 14, September 1984, pp. 27, 38 and 53: the Atari 7800 version in development; the Atari computer version reviewed; the Atarisoft Apple II version reviewed.
- Computer and Video Games issue 68, June 1987, p. 130: Robotron among the Atari 7800 cartridges in Britain.
- For the Williams hardware, the blitters and Vid Kidz, see the Williams Electronics, Defender and Eugene Jarvis entries and their sources.
- historicalsource, “robotron”, GitHub repository created 8 January 2021 (web, secondary): the assembly-language source, no licence stated. https://github.com/historicalsource/robotron