Defender is a scrolling shooter video game developed by Williams Electronics in 1980 and released for arcades in 1981. A side-scrolling shooter, the game is set on either an unnamed planet or city (depending on platform) 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' first video game project and drew inspiration from Space Invaders and Asteroids. Defender was demonstrated in late 1980, before entering production in early 1981. It was distributed in Japan by Taito.
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' 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 purely horizontal scrolling shoot 'em ups. It inspired the development of other games and was followed by sequels and many imitations.
Several ports were developed for contemporary game systems, most of them by either Atari, Inc. or its software label for non-Atari platforms, Atarisoft.
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.
The spaceship (upper right) flies above the surface to protect humans. The minimap shows the entire world.
Defender was Williams Electronics' first attempt at developing a new video game; the company's earlier game was a Pong clone. The popularity of coin-operated arcade games in 1979 spurred the company to shift its focus from pinball games to arcade games. The company chose Eugene Jarvis, who had a successful record of Williams pinball games, to head development. Larry DeMar, Sam Dicker, and Paul Dussault assisted Jarvis. At the time, Williams had a small staff and the management was unfamiliar with technology used for its electronic games. As a result, the staff was afforded a large amount of creative freedom.
The game features amplified monaural sound and pixel graphics on a CRT monitor. A Motorola 6809 central processing unit handles the graphics and gameplay, 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.
Development started by focusing on the game's hardware. The staff first debated what type of monitor to use: black-and-white or color. They reasoned that using advanced technology would better establish them as good designers and chose a color monitor. The developers estimated that the game would require 4 colors, but instead chose hardware that could display each pixel in 16 colors. At the time, the designers believed that 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 game's presentation. Video games at the time relied on hardware to animate graphics, but the developers decided to use software to handle animation and programmed the game in assembly language. The switch allowed them to display more on-screen objects at a lower cost.
The game's control scheme uses a two-way joystick and five buttons. Jarvis designed the controls to emulate both Space Invaders and Asteroids simultaneously. The player's left hand manipulates the joystick similar to Space Invaders and the right hand pushes buttons similar to Asteroids. The button functions also use a similar layout to Asteroids, with the button to shoot projectiles and accelerate on the far right and left, respectively. Jarvis reasoned that players were accustomed to the control schemes of past games, and felt altering past designs would prove difficult for them.
This is the code for the 'Red Label' version of the game, one of four versions distributed to arcades.