Meet the developers still making games for your calculator

Ask any professor, and they’ll probably tell you graphing calculators offer a plethora of mathematical uses, like plotting graphs, inputting trigonometric functions — you know, typical academic stuff. But for many bored students, they have long offered a secondary feature: the ability to play games in class. There are few better ways of skiving off with games like Doom and Portal covertly than tapping away on a graphing calculator — the school-sanctioned gaming system — as a lecturer rambles on about equations.

The history of calculator game development, which only began in earnest in the 1990s, may be recent, but it’s an eventful one. That’s because the graphing calculator is a relatively niche platform that’s not oriented around games, even if the platform has an ardent community of developers — many of whom create calculator games precisely because of the devices’ limitations.

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“I mostly [got started making calculator games] because I was bored out of my mind in class and a graphing calculator was the only electronic device I was allowed to use,” says John Cesarz, a web developer who discovered the hobby through fiddling with a Texas Instruments calculator in eighth grade. “But I kept doing it because I liked the challenge involved with [the] strict hardware limitations the calculator provided.”

Most people may not have heard of Cesarz, though the games he has replicated on the calculator are familiar recent success stories: Wordle, Celeste, and that dinosaur game from Google Chrome. Yet large communities centered around calculator games, such as ticalc.org, Cemetech, and TI-Planet, have been around since the ’90s. That was when graphing calculators started becoming more affordable and prevalent in schools. Among the more popular models used by calculator hobbyists back then was the TI-81, the first graphing calculator released by Texas Instruments, which came with a built-in scripting language called TI-BASIC. This allowed very simple programs to be made.

For Martin Bousquet, this device set the stage for his eventual career as a programmer. Growing up an avid gamer, Bousquet became intrigued by calculator games when his older brother showed him an RPG on the TI-81. At 11 years old, he decided he wanted to make one. “My parents had a computer, but they were really reluctant to me trying [to make my own games] [...] because I broke one of the computers and they were kind of mad at me,” he laughs. That became his first foray into programming, even though he says the TI-81’s rudimentary design rendered game development extremely tedious. “There was no way to get an input without stopping the whole program, so you can’t really make video games. […] You can only make like, multiple choices, like you can only enter a number. Or you can just select a pixel on screen. It’s very, very slow, [but] I was still hooked. I was hooked from the start.”

Calculator game development didn’t immediately take off on the TI-81, since there was no way to transfer data to other devices, so games made were not sharable. That meant all games had to be manually punched in by hand, one button at a time. Yet with the launch of the TI-85 in 1992, games could be shared not just from one calculator to another via a serial port, but to computers as well. What this development meant for the burgeoning calculator community was it could develop and launch games on the calculator that were created via assembly — a much more advanced programming language. Bousquet recounts one of his classmates telling him that using assembly, as opposed to TI-81’s BASIC language, would allow him to make games more effectively. As he didn’t have access to the internet at that time, Bousquet had to head to the library — where the internet was freely available — so that he could learn more about assembly online.

“Back in the ’90s we only had the BASIC language, which was very limited in speed and graphics. [...] z80 assembly allowed you to take almost full control of the hardware, but had a much steeper learning curve,” says James Vernon, another calculator game developer. But one does not simply plonk a game into their TI-85 device; after all, the operating systems in these calculators weren’t made for games in the first place. The trick, as unravelled by illustrious calculator hackers, was to make clever use of exploits in the firmware. This resulted in several assembly shells — programs that allow assembly games to run on calculators — being created by the Texas Instruments community, with the first being ZShell.

But these weren’t the only innovations that emerged from the calculator community. Programmers were also crafting libraries — prewritten code, open-source operating systems, emulators, unique languages, and other tools — so that calculator games could be developed with greater ease.

Even though Texas Instruments wasn’t the only company making graphing calculators — Casio, Sharp, Hewlett-Packard, and NumWorks were also in the mix — Texas Instruments happened to be the most popular brand among enthusiasts. The company’s popularity still persists among calculator hackers today. “The Casio calculators have a large relative French community, but most users today appear to be using TI calculators. I’ve never programmed for the Casios, but from what I’ve seen it tends to be more difficult because of the lack of support,” says developer Matt Waltz.

That said, Texas Instruments has frowned upon the community’s penchant for making games for its calculators over the years, even if some Texas Instruments engineers have been quietly impressed by the community’s efforts. In a New York Times interview from 1999, Richard Schaar, vice president at Texas Instruments, said the company wanted to see if users could figure out the devices’ proprietary assembly language, marveling when students were able to do so handily. “But then kids figured it out [on] their own. They reverse-engineered the assembly language,” he said. At one point, the company even worked with ticalc.org to release calculator games on a CD-ROM, although that was recalled in 2001 due to parents finding “inappropriate content” on it.

With subsequent firmware patches and the release of newer models, it was clear that Texas Instruments didn’t want its calculators tampered with, ostensibly to deter cheating in class. “TI have become more resistant to the community as well, due to the fact that their biggest market is the education sector, and so teachers typically don’t like their students to either be sitting in math class, gaming on their calculators, or using software that’s intended to workaround enforced memory resets before exams,” says Vernon. This culminated in the company wielding its legal weapons with impunity. One prominent example is the issuing of DMCA takedown requests to hackers who published the factors of cryptographic keys to the TI-83 Plus series in 2009, as well as to the forums and websites these keys were published on, which allowed users to run their own operating systems on these devices. These efforts by Texas Instruments were pushed back on, however, when the Electronic Frontier Foundation agreed to take on these cases pro bono on behalf of three hackers who received the DMCA notices.

There have been other attempts by Texas Instruments to halt the progress of calculator games, although hackers have eventually found ways to circumvent them. “TI released an update recently that removed official support for native programming, which the majority of well-known games use. This really hasn’t affected game development that much, since an exploit was quickly found, and it pretty much just amounts to an extra installation step for the end user,” says Cesarz. In the end, these have been largely temporary impediments to the calculator games scene, with developers continuing to make games for these devices. Many relish the challenge of making games on a hardware with relatively limited processing power as compared to modern-day consoles and PCs, which forces them to write code efficiently.

“Limited hardware and limited programming language are probably the main hurdles that one may encounter [when making calculator games],” says Adrien “Adriweb” Bertrand, the co-founder of TI-Planet.org, a prominent French site for Texas Instruments calculators. “If you take the good old TI-83 Plus, then you have a rather slow ancient z80 CPU, a 96 by 64 black-and-white screen, a few 10s of KBs of memory, and very limited features [...] in TI-BASIC. However, it’s got a bit of the ‘bare minimum’ in everything that you’d expect from being able to play good games. You can toggle pixels on the screen, read the keyboard presses, do enough math and logic in the algorithms. That’s basically good enough to make a whole lot of things, even if it’s not powerful.”

Cesarz also points out another quirk of making games for calculators: their highly unconventional hardware architecture. “The TI-84 Plus CE uses an eZ80 processor, and is, to my knowledge, one of the only consumer devices to do so. This means that the majority of the developer tools you can use have been written by others in the calculator community as personal projects, and they often have bugs in them that haven’t been found yet because of how few people are using them,” he says. “You sometimes can’t tell whether a bug is an issue with code you wrote, code that someone else in the community wrote, or code that TI wrote, which makes debugging take longer than on other platforms.”

Image: James Vernon

Image: James Vernon

Even though these can be tedious, such quirks have done little to deter the community from game development. While many developers are content with recreating popular games such as Doom and Among Us on calculators, others, like Vernon, have made original calculator games not released on other platforms. One such title is Banchor: Legend of the Hellspawn for the TI-84 Plus CE. “[Banchor] was inspired by Golvellius on the Sega [Master System], Zelda, and the Diablo series,” says Vernon. “I’d wanted to make a top-down RPG-style game for a while on the calculator. It seemed like a challenging genre to tackle given the limited memory that the calculators had, and I was excited by the storytelling that you can do in an RPG.”

Tinkering with calculators has also introduced developers — many of whom are students and teenagers — to the intricacies of programming. Some have pursued degrees in computer science, while others are now programmers and engineers across various industries. Bousquet is an indie developer creating his own PC games, for instance, running a studio called Blue Noise Games. At the same time, these hobbyists have credited their early interest in programming and career trajectory to their experiences making calculator games.

Even though calculator forums may appear dormant today — many developers from the halcyon days of calculator games in the late ’90s don’t make games anymore, and updates on these sites are less forthcoming than a decade or so ago — the community is still active in obscure corners of the internet. “It’s true that there aren’t as many posts on calculator forums as there used to be, but that’s less because there’s not as much happening lately and more because discussion has moved to less publicly visible Discord channels,” says Cesarz.

Projects around calculator games are ongoing. Bertrand says that he has created a real-time collaborative editor for building programs and games in C and C++, for one. “I’m just so glad to see that the calculator programming community is still alive and well, [even if it’s] mostly on TI [...] and for the fact that we now have such community-made tools available today that we could have only dreamed of in the past,” he says.

Perhaps the community’s enduring presence can be seen as an obtrusive middle finger against the sterile academic ambitions of Texas Instruments, a company that continues, even in recent years, to try to one-up the community from hacking its devices. Or perhaps these hackers are more like defiant rule-breakers: the students openly defying the authorized, long-established customs of learning in schools.

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