New York City--Back arched, one bare foot resting against the other leg's calf, 26-year old Lyman Sheats analyzed the playfield, evaluating risk vs reward. Simply playing the path of least resistance would not do, not in this, the final game of the 1993 PAPA (Professional/Amateur Pinball Association) World Championship Tournament.

Sheats--then a software engineer working for Mitre Corp., Bedford, MA--had methodically marched through the international field of contestants, making it to the final group of four. Steadily building points towards a final crescendo, he captured the championship round to win the tournament's trophy, $3,000, and the admiration of an awe-struck Roger Sharpe, who labeled Sheats "a one-legged impresario, the most highly-focused and disciplined pinball player I've ever seen."

Sharpe should know: A tourney participant and pinball devotee who's played every game that's ever been built since 1967, he literally wrote the book on his favorite subject (Pinball! 1977, E.P. Dutton). Now-a-days, Sharpe and Sheats battle it out head-to-head during coffee breaks at Chicago's Williams Electronics Games complex, where they help design new games for tomorrow's champs.

Mini theme parks. Haven't played the silver ball lately? You're in for a surprise. Pinball in the '90s offers a high-tech playfield, jam-packed with interactive electromechanical and solid-state devices, multi-level ball tracks, plus a wild variety of sound and lighting effects to simulate earthquakes, tornados, and other natural or man-made mayhem. The back glass, more often than not, celebrates hit movies like Twister. Even the actors get involved, their voices immortalized in pinball history. After all, what's Terminator without Schwarzenegger?

Yet, there's more to pinball than meets the eye. It's the guts of the machine that makes today's thematic approach possible. More than 1,000 components, for example, bring life to Attack From Mars, the latest game from Williams, maker of Bally/Midway amusement games. Designing these parts into a tight package, under stringent cost and time constraints, requires the dedicated attention and teamwork of at least five engineers over a nine- to twelve-month span.

"The days of switches and ramps, simple things that could be handled by a set of relays, are long gone," says Brian Eddy, Attack From Mars game designer. Modern games, he explains, transcend the serial-progression, single-player game of the '60s and early '70s. "Now we write a driver for every mechanism, and tie them all into the game's operating system." The result: memory and recall, allowing head-to-head and multi-player games.

As principle designer and project leader, Eddy selects the game's story line, making sure it is cross-cultural and recognizable world wide. Additionally, he specifies all the electromechanical mechanisms and oversees project development. Standard play features, such as jet bumpers and slings, are balanced against new toys like the Martians' flying saucer. "We don't want customers walking up to a new game and saying 'I've seen this before', " Eddy notes.

Likewise, the designer doesn't want the play lasting too long. "A game should take about 2 1/2 to 3 minutes," says Sharpe, director of licensing. "Each ball should average 47 or 48 seconds, and players should win a free game approximately 25% of the time."

Once he has selected the toys, Eddy lays out the playfield on a networked AutoCAD system. Care is taken to distance targets up the incline, or place them along the outside of the playfield to preserve their life without slowing the action. Integrating ball paths and ramps rounds out the play, making the game's overall objective achievable. Eddy likens the design process to squeezing a Disney or MGM theme park into a standardized space.

"You're always thinking of new things the ball can do," he points out. For example, "we might want the ball to be caught between two magnets mid air, spin around this thing, and shoot out that way. Even if we can't make it happen, the process of trying often leads to something we haven't thought of before; that's the excitement of the engineering that goes into these games."

And that makes Bob Friesl "Mr. Excitement." As project engineer, he designs the toys or mechanisms Eddy envisions while laying out the playfield. "The CAD plot I receive from Brian gives me the physical envelope for each mechanism," explains Friesl, a former design engineer with Schwinn Bicycles and the fitness product industry.

Geometry and kinetics. Friesl designs a particular mechanism and its controller using traditional engineering practices, "because you can't look the part up in a catalog." Each device--and there are approximately 150 of them in a game like Attack From Mars--must stand up to an extremely hostile environment: temperatures easily reach 120F, given the abundance of electronics; the balls generate substantial dirt and grime over time; and vibration is a constant.

Every mechanism requires careful analysis of bearing and shaft loads, ball impact, and weld sizes--"real engineering work," states Friesl. "From the operator's point of view," adds Promotion Manager Patrick Fitzgerald, "even one day down is unacceptable; it's a day of quarters not collected."

Once the mechanisms are detailed in 2D, engineers convert the drawings into 3D solid models using SDRC I-DEAS software. They then use these models to generate codes for stereolithography and machining. "Eventually," Friesl predicts, "we will design in solid models to further speed the development and prototyping process."

Three-dimensional models also serve to generate the foam-core or plastic blanks located on the game's white wood--a "shot proving" plywood mockup. That way, Eddy verifies the game's dynamics, making sure the ball moves between the flippers, bumpers, ramps and targets in the desired fashion, utilizing the entire playfield. The white wood also helps determine placement of protective shielding or extra mounting braces to withstand the continual pounding of the ball.

Beyond video. Pinball enthusiasts tend to regard video games with disdain, not because they aren't challenging the first time around, but because their pattern of play can be memorized and mastered. Pinball, on the other hand, is like life itself: you rule a game one day; it bends you over the next.

The game's resurging popularity, however, owes a nod to video. Without a central processing board and proprietary operating system, memory and recall would not be possible. In fact, modern pinball games won't work without programming.

"If there is no software, and I load a ball into the eject slot, it just sits there," says software designer Sheats. "One of the first steps the programmer must do is ensure that the player can kick the ball onto the playfield, and have it return." The procedure, Sheats says, is to program--via assembly language--an instruction set that triggers a solenoid whenever a player activates the eject switch.

Once the game is "flippable," Sheats writes drivers for each of the electromechanical mechanisms. Standard devices like sling shots and thumper-bumpers (targets that provide rebounding action and sound) come free with the operating system. Non-standard mechanisms, like the shaking saucer, require special programming. This is what tailors the operating system to a specific game.

"It's important that Lyman and I work together early on," states Friesl, "because I have to create stuff that our software can support." Programming a moving device, for example, requires hardware able to read the optical encoder on the motor shaft and count the ticks. Otherwise, "we don't know where it is at any given point in the x-y plane."

Other ways the programmer helps keep the quarters coming:

- Write software that will recognize a beginner, occasionally rewarding the player with an extra ball, "in a subtle way to make him or her feel it was earned."

- Develop on-board diagnostics.

- Build "stacked conditions," or multiple events that give the player a chance to double, triple, or even quadruple the reward level.

- Create game rules and choreograph sound, light, and dot-matrix displays.

Lights and music, please. Brian Morris and Adam Rhine create animations for the game's dot-matrix displays, helping bring the storyline to life. Similarly, Dan Forden, the Attack From Mars sound engineer, creates the game's music and sound elements, utilizing a data compression sound board that can run as many as six tracks simultaneously.

Forden pieces together various sound effects and music using sequencing programs and digital audio editing on a Macintosh to control an array of different synthesizers through MIDI (Musical Instrument Digital Interface); Sheats's software programs subsequently tie them to specific game events.

"We need to generate certain sounds for specific shots," says Forden. "For Attack From Mars, we tried to adapt the campy audio of the 1950's-era science fiction movies." What about the horrible gross noises emanating from the aliens themselves? "We taped Doug!" Forden laughs.

Credit Doug Watson, Attack From Mars art director, not only with the Martian voices, but with the game's overall look and intuitiveness. "My job as the artist," he explains, "is to work in conjunction with the programmer, the designer, and the sound engineer, to personalize each shot. Networking these shots graphically makes the game understandable."

From Soho to Brighton. Pinball draws a vast diversity of players the world over. Steve Epstein, owner of New York City's Broadway Arcade near 52nd street, and PAPA tournament founder, sees them all--from celebrities and tourists, to regulars stopping by for a breather after work. He attributes the game's enduring popularity to its live action and unpredictability, recalling an old saying that "the ball is wild."

Maybe so. But for the design engineers who make these machines, it's the little steel sphere, 2.8 ounces and 1 1/16 inches in diameter, that remains constant; everything else is wild.

Arcades and Algorithms

To keep audio on par with the computer-controlled playfields of today's pinball machines, Williams Electronics Games, Inc. recently developed a sound system called DCS, for Digital Compression System. The DCS sound board delivers six channels of 16-bit digital audio for near CD sound quality. Additionally, independent control over the volume, looping, and playback of each channel in response to game commands provides interactivity. A game typically uses one channel for music, and the others for sound effects and speech.

The biggest limitation with most game and multimedia sound systems is storage. For example, 16-bit digital audio at a rate of 31,250 samples per second requires about 60 kbytes of storage per second (a data rate of 500 kbits/sec). Durability requirements dictate the use of ROM for storage of code, images, and sound in arcade games, while the overall cost of the game limits the ROM available for sounds to about 3 Mbytes. The problem is that 3 Mbytes of ROM at 60 kbytes a second is only enough for about one minute of total sound. Most Williams games have between 10 to 15 minutes of non-repeating sound.

Solution: a proprietary, transform coder algorithm that reduces a 500 kbit/sec data rate by a factor of ten or more, and runs on a low-cost DSP chip. This algorithm is similar to those used in the SONY MiniDisc format, the Philips Digital Compact Cassette, as well as emerging digital sound formats for cinema.

DCS hardware is relatively simple. Major components include the surface-mounted DSP chip, eight sockets for ROM, a 16-bit mono DAC, and an audio power amplifier. All this fits on a two-layer printed circuit board measuring about eight inches square.

The low-cost DSP chip--a DSP-2105, manufactured by Analog Devices--runs at 40 MHz and executes more than 10 million complete instructions per second. Three 2-kbyte SRAMs supplement the on-chip RAM. These are mapped into both program and data memory space, and are used primarily as temporary storage for the real-time decompression and the inverse FFT (Fast Fourier Transform) operations required for each of the four playback tracks.

A bi-directional, 8-bit interface connects the soundboard and game host. Playback commands from the game host consist of numbers which the DCS operating system uses as indexes into tables of playlists. One command can trigger anything from a single sound effect to a segment of music that loops indefinitely. Conversely, the sound board can send timed data back to the game host, which is useful for synchronizing animation, display effects, and light shows with music.

Flying saucers, angry aliens

Many of the electromechanical devices built into Attack From Mars are unique to the game and must be designed from scratch. For example, striking the flying saucer with the ball represents a missile attack against an alien ship.

The target, when hit, transmits a signal to the CPU. The processor, in turn, sends an electrical impulse to the solenoid. Energizing the solenoid retracts its armature, impacting the rubber bumper to oscillate the saucer. The electrical impulse to the solenoid is accompanied by activation of a Xenon strobe light, flashing lights in and around the flying saucer, and various sound effects.

Likewise, the CPU sends an electrical pulse--varied in magnitude and duration--to solenoids that shake the Martians. Made from a low durometer rubber, these aliens appear to be jumping up and down, shaking their fists.

TIMELINE FOR DESIGN

- 1871 Cincinatti's Montague Redgrave invents a game which features a spring-powered plunger and playfield.

- 1928 "Billard Skill" introduced. First game to propel steel balls onto a flat playfield.

- 1932 Invention of pinball's "tilt" mechanism.

- 1933 Electricity is introduced to playfield. Also: first automatic payout game where players win cash with high scores.

- 1937 Pinball bumpers appear, adding more speed, excitement, and unpredictability.

- 1941 New York City bans pinball, initiating anti-pinball campaigns across America.

- 1947 The 'flipper" is introduced to emphasize the game's skill aspect and break association with gambling machines.

- 1948 First machine with flipper pair at bottom of playfield.

- 1975 Hybrid video/pinball games appear.

- 1976 NYC and Chicago legalize pinball.

- 1978 Pinball incorporates solid-state electronics.

- 1980 Multi-level playfields introduced.

- 1991 Dot-matrix displays first incorporated.

- 1993 Implementation of digitally compressed sound.