Twilight Zone Pinball: Prototype vs. Production

Twilight Zone Upper Playfield

A Peek at the Game Design Process!

By Ted Estes

Editors Note: Twilight Zone pinball is what many believe to be the pinnacle of pinball design. What is amazing is that the game established this moniker despite having many extras stripped from the production model.

This article originally was featured in the late, great GameRoom Magazine. Ted Estes graciously allowed The GameRoom Blog permission to publish this great piece. Thanks Ted!

The photos are new, as thankfully The GameRoom Blog’s own game room has a sample Twilight Zone pinball machine!

Note there is another article as part of this Twilight Zone series: Twilight Zone Pinball: Romancing the Stone


Amongst the Twilight Zone pinball fans and collectors, one hot topic is the issue of “prototype” games. For some, a prototype game is more valuable, and may even be a status symbol to own. In order to shed some light on this topic, and to give you some insight into the pinball design process, I have catalogued some prototype vs. production games differences for Twilight Zone.

Before we begin our journey, some clarification of terms is in order. To facilitate this, let me start at the beginning of the design process for a new pinball game. The first physical incarnation of a new pinball playfield layout is made with an unpainted piece of plywood. This first playfield usually has been routed for lamp lens inserts, although perhaps not in their final destinations or colors. This first playfield is assembled of hand-made ball guides and other game-specific parts, and is known as a “whitewood.” Several whitewoods may be made for a game as it evolves, and, in general, the final whitewood fairly closely resembles the fully-developed, playable end product (without artwork, and with many hand-made parts, of course). The whitewood (or whitewoods) is used by all the various disciplines involved in game design – mechanical, software, art, etc. – as they work on the components that will go in the final product.

Once the physical design of the pinball playfield and parts has been finalized, enough parts are ordered to build eight or so prototype games. (Back when Twilight Zone was made, ten to fifteen prototypes were usually made. A few more than that were made for Twilight Zone, as extras were needed to showcase the game at the ACME Expo in Las Vegas in the spring of 1993.) If everything is on schedule, the artwork is available for screening on the various playfield parts, the drawings for other parts have been released to vendors, and the resulting prototype games look pretty close to finished “production” games.

The prototypes are put to various uses. The software must be finished, so a prototype ends up in the office of the software developer. Games are needed for play testing, a photo shoot, ship testing, FCC emissions testing, etc. During this final stage of development and testing, changes to the design are inevitably made. Sometimes these changes are small enough or hidden enough not be noticed by the casual player. Other times, significant changes are made.

The next step in the game development lifecycle is to build a small “sample” run of 100-200 games. This sample run serves several purposes, the main one being that pinball distributors need games to put in their showrooms to drum up orders. Additionally, the sample run serves as a way to set up the manufacturing line in preparation for full-blown production.

Twilight Zone Prototypes

With this background information under our belts, we are now ready to explore the events regarding Twilight Zone. To really add to the confusion, Twilight Zone, had two different prototype playfields. The first one is shown on the sales flyer (and the cover of this magazine). Those familiar with the game will recognize that several of the awards shown on the door in the middle of the playfield differ from the production game. These labels resulted from a last-minute brainstorming session where the design team dreamt up names of rules that would be written later – the deadline for the screening of the playfield had come. Only two or three games were made with that playfield version, and at least one of them had the differing text scraped off and replaced with dry-transfer lettering (so as to put the game on location for testing).

The remaining prototypes were made with playfields screened with final version text – with one exception. The final production games have an arrow-shaped lamp in the right loop labeled “Spiral.” This lamp was labeled “Gumball” on the prototypes. As it turns out, the 200 or so sample games were also made with this version of the playfield.

The Bean Counters Attack: Twilight Zone is Cost-Reduced

As you might have guessed, Twilight Zone, was a pretty costly game to build: it was the first wide-body SuperPin™; it has quite a few gadgets; it has extra circuitry to drive extra switches, flash lamps, and magnets. After the prototypes were built, and final cost figures were tallied, cost cutting was the order of the day. The design team struggled to strip out costs where they would not be noticed, and to look for items that were not used or not used much. The scrutiny even went so far as to depopulate the power/driver board to remove the relay and associated circuitry that controlled the old, pre-Fliptronic™, flippers. Some parts, such as the playfield and wiring harness, had already been ordered for the sample games, so some changes did not take effect until after the samples were built. Below, in no particular order, is a non-comprehensive discussion of things that changed.

The Changes

Third Spiral Magnet – The most notable change was the removal of the center (or upper-right) magnet in the Spiral loop. Production games do not have the hole for this magnet, and are screened with the spiral artwork complete. When Pat Lawlor originally designed the game, he was not sure if it would be possible to stop the ball with only one magnet, so he placed two on the right side of the loop – one to slow the ball down, and one to stop it. As it turns out, the magnets were strong enough, and the controlling software could react quickly enough, that catching the ball on any magnet was an easy task. Since the game rules made very little use of the third magnet, it was removed to reduce cost. The presence of the third magnet is automatically detected by the game software, and is used during the Spiral Mode door award. (It is also used by the home ROM software; see last month’s GameRoom article.)

Door Panel Flashers – The circuit board for the door lamps in the center of the playfield was designed to accommodate two small circuit boards for flash lamps under the large door panel lamp inserts. During early play testing, the design team decided that the flash lamps behind the Lock 1 and Lock 2 inserts were very distracting, and misled the player about how many balls were locked. They were removed before prototypes were built. The wire harnesses for the prototypes were already made, however, so that prototype games have the connector for this board. The flash lamps behind the Gum and Ball inserts were removed to reduce cost.

Mini Playfield Changes – Screened text and switch covers were added to the mini playfield during production. Also, a leveling mechanism added. The words “Flip Here” were added to aid in understanding of the MagnaFlip™ feature. (The design team observed players on location staring in slack-jawed confusion once the ball reached the mini playfield.)

Spiral Signs – Originally, there were signs over the left and right Spiral loop shots which read “Collect Next Spiral Value w/Lit.” The left sign was removed because it caused a ball hangup if the wiring was not correctly dressed. The right sign was changed to read “Shoot Here to Load Gumball w/Lit.” In conjunction with this latter change, the arrow-shaped insert at the right loop was changed to read “Spiral” instead of “Gumball.” Most prototype games, and all sample games, have a sticker applied over the old right sign, and the insert has been scraped and relabeled “Spiral” with a decal. (The design team observed some other players on location in clench-jawed frustration trying to figure how to put the PowerBall™ into the gumball machine. After all, it is a bit confusing to have to shoot the right side of the playfield to load the gumball machine located on the left.)

Jet Bumper Posts – Some games have two posts with rubber rings installed in the jet bumpers. The history of these posts is a story of frustration for the design team. In designing Twilight Zone, Pat Lawlor wanted to try something a bit radical, and placed the jet bumpers very close to the bottom of the playfield. After experimenting with the jet bumper placement on the whitewoods, Pat decided that they weren’t too bad down there. Something changed (slight positioning differences of posts and jet bumpers, perhaps?) between the whitewoods and prototypes, however. The ball kept flying down the left drain any time it went into the bumpers. After a few weeks of listening to complaints, Pat came into work one morning, grabbed a drill, some T-nuts, posts, and rubbers, and installed the posts. The complaints died down until several thousand games into the production run. Now, people were complaining that the ball would fly out of the bumpers and straight between the flippers! Something else had changed (slight warp of the playfield, perhaps?). Pat decided to take out the posts, but leave the holes, and put the posts in the coin box for the operator to decide to use. Which setup should you use? Which ever makes your game play the best.

Removed Switches – Several optical switches were removed to reduce cost. The switch from the third magnet was no longer needed, so it was removed. A switch underneath the clock and below the Piano shot was removed, since it was not used for any rules. Also, a second switch was removed from the autofire kicker. It was originally installed so that a ball could be locked on the kicker, and the presence of a second ball could be detected. Game rule complications did not permit locking the ball there, so the switch was no longer needed. Before these switches were removed, Twilight Zone had thirteen optical switches, controlled by two 7-switch boards. After the removal of these three switches, a special 10-switch board was designed for cost savings. Since the board was not ready for sample games, and since the wiring harnesses for the samples were built for the dual board configuration, sample games have the two boards.

Clock Decal – Twilight Zone was produced with two different clock face decals. Many people erroneously believe that the white clock face, as shown in the flyer, indicates a prototype game. In actuality, 2000-3000 games were manufactured with the white clock face. While this is fraction of the production run for Twilight Zone, keep in mind that this number is more than the entire production run for recent games. The real “prototype” clock decal was installed on only two or three of the first prototypes. The decal was very simple, and had six colors in a ring on the face. The colors matched up with six different-colored lamp inserts on the playfield that eventually evolved into the Spiral Award inserts. An early rule that was quickly discarded had the clock running during most of the game. Hitting the Power Payoff target when the hour hand was in a certain colored area of the face would light the corresponding lamp on the playfield. When the rule was changed, the clock decal was not modified. The first decals to arrive looked like something out of a child’s book and received a “thumbs down” from the design team. John Youssi, artist for Twilight Zone, quickly whipped up a new decal, and everyone sighed in relief when the new artwork arrived just in time for the photo shoot. John was unhappy about the plainness of the white decal, though, and did another design later. After the first order of 2000-3000 decals was used up, the new one started rolling off the assembly line.

Lock Lamp – The original Lock lamp was green. (Historically, lock lamps are green.) However, the small arrow was so far from the player, and so tucked under the ramp and clock, that it was very difficult to see. The lamp was changed to a brighter yellow sometime during production.

Leg Levelers – A true prototype game has “platform” leg levelers in the rear. From one game to the next, the playfield pivots may be moved to accommodate large devices on the top or bottom of the playfield. They were moved again on Twiilght Zone. Unfortunately, they were moved far enough that the game could not be adjusted for a correct playfield angle. Special leg levelers were fabricated in the model shop for the prototype games. Production game cabinets have the rear leg bolt holes in a lower position.

Blue PowerBall™ – When Pat Lawlor first envisioned a gumball machine in a pinball game, he wanted it to dispense balls of various colors. Research into a material that would withstand the rigors of a pinball came up with one answer – high temperature ceramic. Unfortunately, this type of ceramic comes in only two colors, blue and white. (Ordinary pigments are not possible, due to the high temperatures involved in the ceramic manufacturing process.) Pat obtained samples of both colors and the design team gathered to throw a ball into a Whitewater prototype. (Whitewater was just finishing development at the time.) The first reaction was “Where did the ball go?” The dark color of the ball made it hide in the shadows. Add to that the dark blue playfield, and the result was an almost invisible ball. So, the decision was made; white was the color of choice. No games were made with a blue PowerBall™.

Identifying Sample and Prototype Games

A true prototype game is easily identified by looking at the lamp circuit boards under the playfield. All prototype circuit boards are red, to distinguish them from production-released boards, which are green.

A sample game is easily identified by the presence of the bracket, core, and routed hole for the third magnet. Even though the magnet and optical switch for the third magnet were not installed on these games, the magnet bracket and core were required, as the playfields were ordered with the holes routed. These games have the connections in the wire harness for installing the third magnet and optical switch, making such a conversion fairly straightforward. (Although not simple – installing the optical switch entails getting access to the mounting spots on the ball guides in the spiral loop.)

Retrofitting the third magnet into a production game is a much larger project, however. There are several obstacles to overcome: the playfield is not drilled/routed for the third magnet and mounting hardware; the optical switch driver board has no support for the extra switch; and the ball guides on the spiral loop are missing the mounting tabs and sighting holes for the extra switch. While it would not be impossible to perform such a retrofit, and I have heard of at least one brave soul doing so, I would not recommend the project.

Ted Estes holds degrees in Electrical Engineering and Computer Engineering from Purdue University and University of Illinois. Before working at Williams Electronics Games, Inc., Ted spent several years working for AT&T Bell Labs. At Williams, Ted was a member of the software development teams for Twilight Zone, Demolition Man, and Roadshow pinballs, and helped out on numerous others.

This post may contain affiliate links. We may potentially earn a slight commission (should you chose to make a purchase using our links). We only promote products we truly believe that are worthy of promotion.