Programmer of Clockwork Worlds
A Scottish programmer who built Transport Tycoon and RollerCoaster Tycoon almost alone in assembly language, turning freight and crowds into small worlds you can read at a glance.
Programmer of Clockwork Worlds
A train clears a junction; a coaster returns with a delighted queue waiting. Chris Sawyer is a Scottish programmer who taught himself machine code on early home computers. He wrote both of these worlds almost single-handedly and almost entirely in x86 assembly language, with Simon Foster drawing the tiny vehicles and people. His games are construction sets that respond. You lay track block by block, then watch cargo, passengers or park guests show whether you built well.
Sawyer grew up in Scotland and started programming as a teenager in the early 1980s. His first home computer, a Camputers Lynx, had no assembler, so he wrote his programs directly as machine code. A Memotech MTX500, which had a Z80 assembler built in, came next. Memotech published games he sent them, and his own site dates his entry into the industry to 1983, writing Z80 code for the MTX and later the Amstrad CPC. He went on to study computer science and microprocessor systems at university in Glasgow.
A job offer from a publisher came to nothing after he graduated, so he cold-called Jacqui Lyons, a software agent. She stayed his representative for the rest of his career. Through her he became a specialist in bringing Amiga games to the PC: Logotron’s StarRay in 1988, David Braben’s Zarch (published on PC as Virus), Campaign, Birds of Prey, Dino Dini’s Goal and, in 1993, Frontier: Elite II. For that last game he added texture mapping, using what he later called “tricky self-modifying code” to keep it fast.
Porting meant fitting someone else’s design onto a different machine, one processor instruction at a time. Sawyer did it in Intel assembly language. Jimmy Maher’s history notes that he refused to write in a high-level language and never changed his mind. This is our reading rather than his stated rationale: that discipline is what later let thousands of vehicles and visitors move at once on an ordinary 1990s PC.
Transport Tycoon started from two side interests. Sawyer was playing Sid Meier’s Railroad Tycoon and, for fun, building an isometric 3D engine. “The two interests sort of collided,” he told Arcade Attack in 2018. Looking back in 1999, he said he had hoped to move the genre on with isometric graphics, several kinds of transport and rival companies whose vehicles you could actually see. In 2002 he described the aim as “a world which seemed to be living and breathing.”
He built the game himself and showed it to publishers when it was more than half finished. He signed with MicroProse because he felt its staff supported him best. Its producer asked for a schedule, and Sawyer’s estimates added up to more than two years of work. He divided them by four and delivered the game four or five months later. Simon Foster, a freelance artist, replaced Sawyer’s rough graphics with the finished vehicles, towns and animation. John Broomhall, MicroProse’s in-house composer, wrote the jazzy score. MicroProse’s British office suggested naming it Transport Tycoon so that it sat beside Railroad Tycoon. It came out in 1994, followed by a World Editor add-on and, at the end of 1995, Transport Tycoon Deluxe.
Underneath the trains, a precise rule decides where cargo goes. The Deluxe manual explains that a station only collects from industries and town buildings within four squares of it. When rival stations share a catchment area, the cargo is divided between them by their ratings. A station’s rating rises when vehicles call often and when they are newer and faster. It falls when goods or passengers are left waiting. Carrying cargo farther pays more per trip but takes longer, and ageing vehicles end up costing more than they earn through breakdowns and the traffic jams they cause. So a network is a set of service promises. If you neglect a station, a competitor’s trucks can take its coal.
The design had real weaknesses. Maher argues that money stops mattering once a company is established, and that replacing ageing vehicles turns into busywork. Sawyer himself said in 2004 that he had never been happy with the AI of the rival companies. Still, he said in 1999 that the game had sold well over 600,000 copies, when his own “high hopes” had been a few thousand. That success also changed how he worked. He was very active with fans online in the mid-1990s, but in 2016 he said that it started to “take over”. Afterwards he largely stayed out of the discussions so that he could keep designing with a free hand.
The theme park began as a detour. Sawyer spent most of 1996 writing new code for Transport Tycoon 2. In 2018 he described having had “a crisis of confidence” about whether it would be a big enough advance, and the project was shelved in August 1996. By then he had been to a couple of small theme parks with friends and had been leafing through the photographs in the book White Knuckle Ride. As a side experiment, he put a simple coaster into the new engine. RollerCoaster Tycoon, he said in 2004, “started off as just an experiment using Transport Tycoon 2 game code.” It shared nothing with the first game, though. In 1999 he explained that a park needed tracks, paths and other objects stacked at several heights on the same square, which required a completely different map structure from Transport Tycoon’s single layer.
The publishing arrangements changed as well. When Sawyer described a roller-coaster game to people in the industry, the response was “so dismissive” that he decided to build the whole thing independently. He worked on it for about a year and a half before approaching anyone. Hasbro Interactive took it on, and Sawyer hoped a company with a toy business would understand a game that plays like a toy. When Hasbro later bought MicroProse, the Tycoon name became available. Because the game was almost finished before any publisher saw it, and because Jacqui Lyons at Marjacq negotiated hard to protect his rights, Sawyer kept ownership of the series. He said in 2000 that Simon Foster was the only other full-time member of his team. The 1999 manual credits Allister Brimble for sound and music and FISH (UK) Ltd for additional programming. It also thanks the ride designer John Wardley, the European Coaster Club and others for help with research and testing. Sawyer wrote the game about 99 per cent in x86 assembly with Microsoft’s Macro Assembler, using a small amount of C to talk to Windows and DirectX.
The coasters are a construction kit. Sawyer explained in 2002 that every track piece has to line up with the map squares and every inversion has to meet set 3D coordinates so that all the pieces plug into each other. After a test run, the manual explains, the game gives each ride three ratings: excitement, intensity and nausea. Intensity is calculated from the forces, accelerations, inversions and speed a rider experiences. Push it past ten and no one will ride, “even for free.” Scenery near the track raises excitement, especially when it creates the illusion of a near miss. Guests then decide for themselves, based on their own tolerances, and the Guest Info window shows what each one is thinking. “Listen to the guests!” Sawyer advised in 2000. “You can’t force the guests to go on rides they don’t like.” The difficult part, he told GameSpy in 2002, was keeping each guest’s decisions simple and fast enough for a park of more than 5,000 people, even though that meant some of them would get lost.
RollerCoaster Tycoon was released in March 1999, followed by two expansion packs. The sequel, published by Infogrames in 2002, kept the same look but added larger maps, vertical scenery, a scenario editor and saved ride designs that include their scenery. Foster and Brimble were credited again. Looking back in 2016, Sawyer named RollerCoaster Tycoon 2 as the game he was proudest of as a design. He said Frontier Developments, David Braben’s company, made its later expansion packs.
Sawyer had been starting and abandoning new transport games since 1996. After RollerCoaster Tycoon 2 he concentrated on one, again developing it without publisher input until he was sure it would work. Before Locomotion came out, he told GameSpot that the fun of both Tycoon games was “50 percent in the construction process and 50 percent in world-watching.” He kept a fixed isometric view so that everything stays visible at full detail, “a bit like looking down at a tabletop train set.” He also said that roughly a hundred times more processing power had finally let him build stronger rival companies than the ones in Transport Tycoon, which had never satisfied him. Atari released Chris Sawyer’s Locomotion in October 2004.
That same year, Frontier made RollerCoaster Tycoon 3 in full 3D, with Sawyer as a consultant. He later explained that adding detail with a 3D viewpoint and removing the block-like restrictions was the logical next step, but that he could not get excited about taking the game in that direction. He handed the series to people who were. Locomotion sold poorly, and reviewers were unkind. Sawyer still calls it “the best piece of programming I’ve ever done.” He partly blames weak marketing and support, but he also concedes that it lost the simple, restrictive play that made Transport Tycoon work. Going back to Locomotion after Transport Tycoon shows how much a little added complexity can change a game of watching.
After 2004 Sawyer stopped making new games. In 2016 he gave his reasons. He had spent nearly twenty years working 16-hour days, he had run out of inspiration for new games, and he disliked both the industry’s turn towards violent games and the large teams it now needed. A dispute with Atari also contributed. In 2005 he sued the publisher over about $4.8 million in royalties he said he was owed, alleging among other things that his auditors had been refused access to its 1999–2001 accounts. Atari counterclaimed over a RollerCoaster Tycoon demo that Frontier had made. The case was settled out of court in February 2008 on confidential terms. Sawyer said later that it “soured my view of the whole games industry.”
The older games found new platforms through his partnerships. Sawyer and Jacqui Lyons founded 31X Ltd. Its partner studio Origin8 rewrote Transport Tycoon for phones and tablets in 2013, because, Sawyer explained, the original 8086 assembly “can’t be recompiled for other platforms.” RollerCoaster Tycoon Classic followed. In 2016 Sawyer said he owned the RollerCoaster Tycoon intellectual property and trademarks and licensed Atari to make new games, while keeping deliberately clear of their design. In November 2024 Atari announced that it had acquired Transport Tycoon from him.
Players kept the games going too. OpenTTD, a free, GPL-licensed game based on Transport Tycoon Deluxe, and OpenRCT2, an open-source re-implementation of RollerCoaster Tycoon 2, keep both designs playable on modern machines. Sawyer has described a “Lego-like philosophy” behind his work: “you build things block-by-block in a rather simplistic and restrictive environment,” then keep the models running. He says the games have become bigger than he is, and he prefers “to let the games do the talking.”
