Developer Profile: Jeff Tunnell of Spotkin

Contraption Maker

Spotkin’s physics-based, endlessly creative sandbox makes players a different kind of trigger-happy


Jeff Tunnell is something of a legend in the PC gaming world, having founded classic PC developer Dynamix in Eugene, Oregon back in 1984. He later went on to co-found successful game startups like GarageGames and PushButton Labs, both of which he eventually sold. Now, some 30 year later—along with former partners of PushButton Labs, GarageGames, and Dynamix—he’s back in the same city making a follow-up to one of his greatest achievements: The Incredible Machine.

Tunnell’s new studio, Spotkin, includes much of the original team that developed The Incredible Machine back in its Dynamix days. The new title, Contraption Maker is very much the spiritual successor to that game, but modernized for big screens and processors and better in every way. “In spite of working on big game titles like Tribes and Starsiege, and creating two companies with successful exits to IAC and Disney, The Incredible Machine was always the favorite game that we worked on,” Tunnell says. “We’ve built a technology platform to create an entire line of games like Contraption Maker that interoperate like software Legos.”


Before starting on development, Tunnell and his team made an extensive engine comparison chart, which ultimately led their selection of Cocos2d. In a previous life, Tunnell was co-founder of GarageGames, which essentially created the indie game engine market with its $100 Torque Game Engine back in 2001. “I didn’t really want to be back in the technology creating business—I just wanted to make games,” says Tunnell. “I thought it would be a no-brainer to use Unity for our game. However, upon more research—this is back when we first started Spotkin, about three years ago—we decided against Unity, because there is no available source code, [at least] for a reasonable price. The deployment to mobile is painful, and the size of the executable is too large. There are many more reasons that are beyond the scope of this short interview—some day, I’ll write a blog about this subject.”



All told, Contraption Maker has been in development for over three years. The first year was spent building up a technology platform, of which Cocos 2D-x is a part; the second year was getting the game to Early Access on Windows, OSX, and Linux releases on Steam and Humble; the third year has been releasing version 1.0, and finishing up its Steam Workshop-like service for sharing puzzles, contraptions, and mods. Now, the team is in the process of finishing up the Android and iOS versions of its game. “While Cocos 2D-x is cross platform and the underlying C++ code runs on all of these platforms, the user interface and UX needs to be quite different on these devices,” he says.



Tunnell explains that Spotkin is primarily using Cocos as a rendering and platform layer, to remove its higher level C++ code from platform dependencies. “We’ve built our own GUI, networking, physics scripting code, and services like installer and updaters, teacher dashboard—things like that,” he explains. “We consider these assets to be the source of some of the biggest value in our company, and it is essential that these assets do not access proprietary libraries or APIs that we don’t have source code to, or can’t control on our own if need be.” At the end of 2014, the team ported up to Cocos 2d-x 3.0 to set itself up for 3D assets in its 2D world.

Currently there are six core people in Spotkin, who effectively handle the entirety the game’s core coding. All together, there have been roughly 30 people at work on Contraption Maker over the course of its three-year development cycle, from artists to sound designers and other contractors.



Tunnell says that the most difficult programming task for Spotkin has been the creation of its custom deterministic physics engine. One of the studio’s programmers, Kevin Ryan, started with the amazing Chipmunk Physics, and rewrote the entire thing into integer math; he did this to keep the small discrepancies in math coprocessors from changing the outcome of the game’s physics puzzles and contraptions on different processors and devices. “Although this is a world-class achievement, most users will never know because they don’t know it is a problem,” Tunnell says, with a chuckle. “But oh well—such is the price for perfection.”

Despite having worked on huge AAA games such as Tribes in the past, Tunnell says his team has essentially been in the indie space for fifteen years now. “We’re used to working with small teams,” he says, of developing high-quality productions with relatively undersized teams. “The only limitation is time. There are always more ideas than time or money permits, but a small team of world-class people can achieve huge results when there are great technologies such as Cocos to build upon.”

Be sure to check out Spotkin’s Contraption Maker online at

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