The Golden Age of Computer Gaming

Chapter 2: The Sierra Revolution

← Previous: Chapter 1 | [Series: Chapter 2 of 12] | Next: Chapter 3 →]

The Sierra Revolution

THE FUNDAMENTAL LAW

In a small town called Oakhurst, California, in the shadow of Yosemite, Ken and Roberta Williams weren't just making games - they were creating a new language of interactive entertainment.

THE MOMENT OF CREATION

Picture this: 1979. Ken Williams takes a teletype terminal home to work on an accounting program. Looking through a catalog, he finds a game called Colossal Cave Adventure. He buys the game and introduces it to his wife, Roberta, and they both play through it together. They begin to search for something similar but find the market underdeveloped.

Roberta decides that she could write her own adventure, conceiving the plot for what would become Mystery House. She takes inspiration from Agatha Christie's novel "And Then There Were None" and the board game Clue, which helps break her out from a linear structure. Recognizing that though she knows some programming, she needs someone else to code the game, she convinces her husband to help her.

Ken agrees and borrows his brother's Apple II computer to write the game. Ken suggests that adding graphical scenes to the otherwise text-based game would make it more interesting for players, so the couple buys a VersaWriter machine - a device that could trace drawings and convert them into digital coordinates.

THE ART OF INNOVATION

Ken finds that the resulting digital drawings are too large to fit into a 5¼-inch floppy disk, so he devises a way to convert the images into coordinates and instructions for the program to redraw the lines of the scenes rather than static images. He also writes a better version of the VersaWriter scanning software, creating the first graphics system for adventure games.

The resulting game is a text-based adventure with a depiction of the character's location displayed above the text. Ken spends a few nights developing the game on his Apple II using 70 simple two-dimensional drawings done by Roberta. The game's code is completed in only a few days, finishing on May 5, 1980.

FROM THE ARCHIVES

The couple takes out an advertisement in Micro magazine as On-Line Systems, and mass-produces Ziploc bags containing a floppy disk and a sheet of instructions, to be sold at $24.95. To the Williamses' surprise, what Roberta had initially considered a hobby project sells more than 10,000 copies through mail-order.

Roberta personally packs the disks and supporting materials in Ziploc bags, and answers her home phone to provide hints for the game's puzzles. Ken begins to personally distribute copies of the game to computer stores, with hopes that it would allow the couple to eventually move out of the city.

THE PERFECT TIMING

Mystery House becomes an instant hit with about 15,000 copies sold, earning $167,000. It is the first computer adventure game to have graphics, although made with crude, static, monochrome line drawings. The success shifts their focus to developing more graphical adventure games, and Mystery House becomes the first in what would be called the Hi-Res Adventure series.

Though Ken believes that the gaming market would be less of a growth market than the professional software market, he perseveres with games. In 1980, the Williams found On-Line Systems, which would become Sierra On-Line in 1982. They release Wizard and the Princess later that year, improving on their previous title with color graphics and dithering. The game sells 60,000 copies, leading them to hire more employees for distribution and programming.

THE TECHNICAL DANCE

Early Sierra games perform a delicate ballet of resources, operating within severe constraints. Their Hi-Res Adventure series continues through 1981 and 1982 with Mission Asteroid, Cranston Manor, Ulysses and the Golden Fleece, Time Zone, and The Dark Crystal. Like Sierra's earlier adventure titles, such as Wizard and the Princess, these games use vector graphics rather than pre-rendered bitmaps, which would consume excessive disk space on 360-kilobyte floppy disks.

Each screen is drawn line-by-line and painted in, with the games drawing polygons on the screen and then coloring them. This technique would become standard in all Sierra adventure games up to King's Quest V, proving that technical limitations could inspire elegant solutions.

THE IBM PARTNERSHIP

In late 1982, IBM contacts Sierra On-Line for launch games for its forthcoming PCjr home computer, announced in November 1983. IBM offers to fund the entire development and marketing of the game, paying royalties. Ken and Roberta Williams accept and start on the project, with IBM requesting a sophisticated and replayable adventure game.

Roberta Williams creates a story featuring classic fairy-tale elements, based on an earlier On-Line Systems title called Wizard and the Princess. Her game concept includes animated color graphics, a pseudo 3D-perspective where the main character is visible on the screen, a more competent text parser that understands advanced commands from the player, and music playing in the background through the PCjr sound hardware.

THE BIRTH OF AGI

For the game, a complete development system called Adventure Game Interpreter (AGI) is developed. The original King's Quest engine and language, initially named Game Adaptation Language by its designer Arthur Abraham, is created specifically to showcase the technology of the IBM PCjr. AGI is originally developed by IBM but donated to Sierra when IBM is unable to finish the project due to the dismissal of its main designer.

To create the interactive animation, the King's Quest development process deploys a prototype version of what would eventually become the AGI game engine. In addition to designer and writer Roberta Williams, six full-time programmers work for 18 months to complete the game. IBM pays for much of the $850,000 development cost.

Here's what AGI script looked like—a custom scripting language that let designers create interactive scenes without low-level programming:

// King's Quest I - Getting the dagger from the tree stump
// AGI Logic Script circa 1984

if (said("look","stump")) {
  print("You see a small hollow inside the stump.");
}

if (said("look","hollow")) {
  if (f5) {  // dagger already taken
    print("The hollow is empty.");
  }
  else {
    print("Inside the hollow you can see a dagger!");
  }
}

if (posn(ego, 15, 45, 20, 50) &&  // Player near stump
    said("get","dagger")) {
  if (!f5) {
    get("dagger");
    set(f5);  // Mark dagger as taken
    score += 2;
    print("You take the dagger from the hollow.");
  }
  else {
    print("You don't see a dagger here.");
  }
}

This abstraction was revolutionary—designers could focus on storytelling and puzzle logic while the AGI engine handled animation, collision detection, and cross-platform compatibility.

THE REVOLUTIONARY RELEASE

In mid-1984, King's Quest: Quest for the Crown is released to much acclaim, beginning the King's Quest series. IBM states in advertisements that King's Quest "runs on the IBM PCjr and makes good use of some special PCjr capabilities," with "unusually smooth and realistic" animation and "an impressive variety of sound effects."

The original PCjr version includes ambient sounds that would later be removed from other ports. Crickets can be heard around Daventry, the troll makes stomping noises across the bridge, the goat bleats, the ogre growls, the river can be heard, and splashes occur when the character falls into water. These atmospheric touches create an unprecedented sense of place in a computer game.

THE PERFECT PARADOX

Due to the PCjr's poor reception, King's Quest does not sell very well initially. IBM's discontinuation of the computer in March 1985 stuns Sierra. However, later that year Tandy Corporation releases the Tandy 1000, an IBM PC compatible that succeeds where the PCjr failed. With the advantage of the development system, Sierra is able to quickly release versions for the Tandy 1000, standard PCs, and the Apple IIe, which helps propel sales.

King's Quest causes a sensation in the burgeoning market of PC-compatible computers, and Sierra sells more than half a million copies. The game proves that vector graphics can create compelling animated adventures, that music and sound effects enhance immersion, and that players want to see their character moving through the world.

THE EVIDENCE OF SUCCESS

The game introduces several revolutionary concepts that would define adventure gaming for years to come. Players control Sir Graham (originally "Grahame" in the PCjr version) as a visible character who can walk around the screen, climb trees, swim across moats, and interact with the environment in real-time. The AGI engine supports 16-color graphics, three-voice sound, and sophisticated animation routines that bring the fairy-tale world to life.

King's Quest establishes Sierra's reputation for technical innovation combined with strong storytelling. Unlike text adventures that required players to imagine everything, or arcade games that prioritized action over narrative, King's Quest proves that computers can tell visual stories that engage both mind and eye.

THE TECHNICAL ACHIEVEMENT

The AGI engine represents a breakthrough in adventure game technology. It draws graphics in an off-screen data buffer, then blits them into video memory, preventing the game from revealing hidden objects while drawing the screen. The engine is principally developed for 16-bit computer architectures, including IBM PC compatibles, the Atari ST, Commodore's Amiga series, and Apple's Macintosh computers.

Sierra also ports AGI to three 8-bit computer models: the TRS-80 Color Computer, the Apple IIe, and the Apple IIc, proving the engine's flexibility across different hardware platforms. This cross-platform approach allows Sierra to reach the widest possible audience while maintaining consistent gameplay experiences.

WISDOM OF THE REVOLUTION

The success of King's Quest transforms Sierra from a small company making simple adventure games into a major force in the computer game industry. The AGI engine becomes the foundation for Sierra's adventure game empire, powering fourteen games between 1984 and 1989. More importantly, it establishes the template for graphic adventure games that would influence the entire industry.

By the end of the 1980s, however, AGI's 160×200 resolution begins to look outdated and cannot keep up with newer developments such as mice, which are used extensively by competitor LucasFilm Games' SCUMM engine. This technological pressure would eventually lead Sierra to develop the more sophisticated Sierra's Creative Interpreter (SCI) engine, but AGI's legacy as the foundation of graphical adventure gaming remains secure.

THE PERFECT FOUNDATION

Ken and Roberta Williams have proven that games can be more than text, more than simple graphics, more than basic entertainment. They have shown that computers can create interactive fairy tales where players become the heroes of their own stories. From Mystery House's simple line drawings to King's Quest's animated adventures, Sierra has established the visual language of adventure gaming.

The revolution is complete, but this is only the beginning. With AGI proven and successful, Sierra can now explore new worlds, tell bigger stories, and push the boundaries of what adventure games can achieve. The foundation is laid for an empire of imagination that will define computer gaming for the next decade.