Defender is a 1981 horizontally scrolling shooter video game developed and published by Williams Electronics for arcades. It was released in Japan by Taito. It is set on an unnamed planet where the player must defeat waves of invading aliens while protecting astronauts. Development was led by Eugene Jarvis, a pinball programmer at Williams; Defender was Jarvis's first video game project and drew inspiration from Space Invaders and Asteroids. Defender was demonstrated in late 1980 and was released in March 1981.
Defender was one of the most important titles of the golden age of arcade video games, selling over 55,000 units to become the company's best-selling game and one of the highest-grossing arcade games ever. Praise among critics focused on the game's audio-visuals and gameplay. It is frequently listed as one of Jarvis's best contributions to the video game industry and one of the most difficult video games. Though not the first game to scroll horizontally, it created the genre of horizontal scrolling shoot 'em ups. It inspired the development of other games and was followed by sequels and many imitations.
Ports were developed for contemporary game systems, most of them by either Atari, Inc. or its software label for non-Atari platforms, Atarisoft. The 1982 Atari 2600 version was one of the best-selling games for the system and sold over 3 million cartridges.
Gameplay
Defender is a side-view, horizontally scrolling shooter set on the surface of an unnamed planet. The player controls a spaceship flying either to the left or right. A joystick controls the ship's elevation, and five buttons control its horizontal direction and weapons. The player starts with three "smart bombs", which destroy all visible enemies. As a last resort, the "hyperspace" button works as in Asteroids: the player's ship reappears in a random—possibly unsafe—location. Players are allotted three ships at the start of the game; another ship and smart bomb are awarded every 10,000 points (adjustable per machine). Two players can alternate turns.
The object is to destroy all alien invaders, while protecting astronauts on the landscape from abduction. Landers pick up humans and attempt to carry them to the top of the screen at which point they turn into fast-moving mutants. A captured human can be freed by shooting the lander, then catching the human before it falls to its death, and dropping it off on the ground.
Defeating the aliens allows the player to progress to the next level. Failing to protect the astronauts, however, causes the planet to explode and the level to become populated with mutants. Surviving the waves of mutants results in the restoration of the planet. A ship is lost if it is hit by an enemy or its projectiles, or if a hyperspace jump goes wrong (as they randomly do). After exhausting all ships, the game ends.
Development
Defender was Williams Electronics' first attempt at developing an original video game; the company's earlier game was a Pong clone. The popularity of coin-operated video games in 1979 spurred it to expand beyond pinball games. The company chose Eugene Jarvis, who had a successful record of Williams pinball games, to head development. Additionally, the release of Taito's Space Invaders in 1978 inspired Jarvis to pursue arcade game development. Larry DeMar, Sam Dicker, and Paul Dussault assisted Jarvis.
Development began around October 1979. The team first determined the specifications of the game's hardware. They aimed to portray Williams games as technologically advanced and included more capabilities than the game required. At the time, Williams had a small staff and its management was unfamiliar with the technology used for its electronic games. As a result, the developers were afforded a large amount of creative freedom. They used a Motorola EXORciser computer to develop the game's program.
Early designs and conception
Initially, Jarvis spent 3–4 months developing color variations of Space Invaders and Atari, Inc.'s Asteroids. Space was a popular setting for video games at the time, and Jarvis felt the abstract setting would help obscure simple graphics. First inspired by Space Invaders, he created a prototype with similar gameplay that included new mechanics. After spending a few weeks with the design, however, the team felt it was dull and abandoned the idea. Development then shifted to emulating Asteroids, which displays vector graphics on a special monitor, and the team experimented with recreating the game with pixel graphics. They abandoned this design as well, deeming it a poor recreation and visually unappealing.
Believing the first attempts to be too derivative, the developers held brainstorming sessions. During a session, they agreed that one of Asteroidss favorable elements was its wraparound screen effect. They felt that allowing the player to fly a ship off the screen would be exciting and decided to create a game world larger than the screen displayed. The game's environment was made wider than the screen and scrolled horizontally. Expanding on the idea, they envisioned Space Invaders design rotated 90 degrees to have the ship move up and down while flying horizontally. Large asteroids, an element from Asteroids, were added to the game world but later removed. Jarvis intended the screen to scroll only from left to right; fellow Williams employee Steve Ritchie, however, convinced him the game should be able to scroll in either direction.
After six months of development, the team considered the progress insufficient. They examined other games and concluded that survival was a necessary component. The team devised enemies to present a threat, the first of which was the "Lander". Jarvis enjoyed violent, action entertainment, and he wanted to include those elements but felt the action should have a reasonable objective. Inspired by the 1960s television show The Defenders, Jarvis titled the game Defender, reasoning that the title helped justify the violence. He added astronauts to expand on the space theme and give the player something to defend while shooting enemies. Jarvis believed the combination of offensive and defensive actions created a "rich tactical and strategic experience" that forced the player to frequently evaluate the situation's priorities. He further noted that the added complexity made the gameplay less monotonous, which differentiated it from other games that solely rely on a relentless battle that eventually kills the player character.
The element of flying over a planetscape was added after a brainstorming session between Jarvis and Ritchie. The landscape is depicted as a line only a pixel wide, primarily because the hardware was not powerful enough to generate anything more detailed. The background stars' movements were made slower than the ship in order to create a sense of depth.
Refinement and completion By July, development was behind schedule and Jarvis's supervisor pressured him to finish the game to display at the then-upcoming Amusement & Music Operators Association (AMOA) trade show in September. Jarvis spent several weeks creating the astronauts, which his boss wanted to omit if the process didn't hasten. The pressure frustrated Jarvis to the point he considered resigning. Around that time, Sam Dicker was hired as a new programmer. He assisted in programming the game and added audiovisual effects. Dicker implemented a particle effect algorithm to generate unique explosions when enemies were destroyed. The new elements re-invigorated Jarvis, who felt the project began to show promise.
Development then shifted focus to the enemies. Landers were given the ability to capture humans, and a new enemy was devised from the mechanic: "Mutants", captured humans that had turned hostile. The Mutants added a rescue element that Jarvis believed made the game more interesting and would encourage the player to continue playing. He applied the element of making a "comeback" to the planet and restored it and the humans after surviving five waves following the planet's destruction; Jarvis felt it mimicked the ups and downs of real life. "Bombers", enemies which release floating bombs on the screen, were added next. More enemies were added to create different gameplay elements. "Swarmers" and "Pods" were designed to attack the ship rather than the astronauts. "Baiters" were included prevent the spaceship from lingering and add pressure to the player. Based on a similar enemy in Asteroids, Baiters quickly follow the ship to collide with it.
Defender remained unfinished by September, and almost every Williams programmer assisted with meeting the deadline for the AMOA trade show. The evening before the trade show, the arcade cabinets were delivered for display. However, the developers realized they had not created an attract mode to entice an audience and a high score system. After measuring how much space was available in the system's random-access memory to patch the program, they began working on those components that night. DeMar coded the attract mode, Dussault and Dicker created the high score table, and Jarvis playtested and fixed bugs. Early the next morning, the team created the final EPROM chips and installed them in a prototype board. As they improperly installed the chips, the game did not start and soon caught fire. After diagnosing the issue, the team created a new set of EPROMs and successfully activated the prototype. Once the components were operational, the team returned to their homes to prepare for the show.
After the AMOA trade show, the developers expanded the game to allow users to play indefinitely. The display model included five levels, which the team felt was more than enough because of the game's difficulty; most Williams employees could not progress past the third level and Jarvis's score of 60,000 points seemed unbeatable to them. While they believed it unlikely, the developers added more levels that repeated in order to be prepared for players that might exceed their expectations; they felt the game would be boring after level five otherwise.
Hardware
The game features amplified monaural sound and pixel graphics on a CRT monitor. The machine consists of five circuit boards that coordinate different processes required to operate the game: a main central processing unit (CPU), a read-only memory (ROM) board, a soundboard, an interface controller board, and the power supply. A Motorola 6809 microprocessor acts as the CPU to execute the game code and assemble the graphics to display on the screen, while a Motorola 6800 microprocessor handles the audio. A pack of three AA batteries provide power to save the game's settings and high scores when the machine is unplugged from an electrical outlet. The cabinet artwork is stenciled on the wooden frame.
When planning the hardware specifications, the staff first debated whether to use a black-and-white or color monitor. They chose a color monitor, reasoning that advanced technology would better establish them as good designers. The team estimated that the game would require 4 colors but chose hardware that could display each pixel in 16 colors. At the time, they believed this was more than they would ever need for a game. The monitor's resolution is 320×256, an expansion from the then-industry standard of 256×256. The staff believed that the wider screen provided a better aspect ratio and would improve the presentation. Video games at the time relied on hardware components to animate graphics, but the developers decided to handle animation via software and programmed the game in assembly language. The switch allowed them to display more on-screen objects with less processing power.