Garriott doesn’t necessarily look like someone who helped revolutionize video games back in the medium’s earliest days. Compared to most computer game pioneers of the ’70s, he appears far too young to have launched one of the most formative and influential computer games ever made. Yet he designed his first game in 1977. His breakout hit, Ultima, launched a few years later, right as America was collectively calling in sick to work due to Pac-Man Fever. There’s no denying the influence of Garriott’s work over the past four decades.

Of course, there’s a reason for Garriott’s relatively youthful appearance: He was still a teenager when he made his RPG debut. His prodigious aptitude for multiple disciplines—design, programming, and storytelling—blossomed against a backdrop of the fantasy genre’s explosive popularity in the U.S. during the 1970s. All these factors came together to inspire Ultima.

As the creative visionary behind Ultima, Garriott can arguably claim responsibility for more medium-defining works than any other game designer outside of Nintendo’s Shigeru Miyamoto. Along with Sir-Tech’s Wizardry: Proving Grounds of the Mad Overlord and Atari’s Adventure, Ultima laid the groundwork for how role-playing games should work on personal computers—and, eventually, on consoles. The influence of the Ultima games, and 1983’s Ultima 3: Exodus in particular, reached far beyond the U.S. market. They guided a generation of Japanese and European designers as they ventured into the role-playing genre with works of their own.