When the 29-year-old Samuel Rizzon is asked what he does, he answers with a single word: “developer.” While accurate, it’s a modest label for someone whose work has stretched well beyond writing code.

At an age when many engineers are still settling into a single specialty, Rizzon has built products embraced by large enterprises, online classrooms, and the open-source community, three arenas that rarely reward the same instincts. His is a story of versatility, of an engineer who has never been willing to be only one thing.

From a bedroom app to a billion documents

Interested in technology and building software from a young age, Rizzon developed and shipped his first product at 19: a Bible quiz he published to the Play Store and the App Store in 2015. It picked up 22,000 downloads, and that response was enough to convince him that making things people actually used was worth pursuing. Not long after, he joined TOTVS, Brazil’s largest technology company, where he would spend the next five years and lay the foundation of his career.

That foundation took shape around a single product. It started as a proof of concept for one client that wanted a way to sign documents digitally. Rizzon wrote it from scratch, and the prototype worked well enough to become a product in its own right. It grew into a standalone electronic signature platform comparable to DocuSign, and today it processes more than a billion documents for over a million customers.

Building it was largely a solo effort. Working before AI coding assistants existed, Rizzon architected the whole stack himself, from an Angular front end and a C# back end to a Chrome extension and a desktop application that reverse-engineered the physical A1 and A3 devices Brazilians use to authenticate documents. As the product matured, a team formed around him, eventually reaching roughly 10 engineers, designers, and product staff, with Rizzon leading the work that turned the prototype into a full product line.

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From there he spent a year at the consultancy CI&T before taking a remote role as a full-stack engineer for a New York startup, a job that gave him his first direct contact with the U.S. technology scene.

Gaining experience as a founder

Around the same time, Rizzon set out to build a company of his own. He ran it out of his room in Brazil, without investors, without a team, and without a network to lean on. What he had was persistence, and it showed: he took the business from nothing to 30 paying customers across Brazil, the United States, and Ireland, with 8,000 people using its web app.

Since there was no one else to do it, he handled sales, client conversations, support, and marketing himself, the parts of a business most engineers never touch. He even started a YouTube channel during this period, which grew to 3,000 subscribers.

He doesn’t romanticize how hard it was, and he is especially frank about the difficulty of doing it from Brazil, far from any real startup network. “I had nothing, really nothing,” he points out. “It was just me in my room. Creating something and trying to sell it and reach customers. It was a very specific niche, and it was a hard niche.” That isolation forced him to operate on his own, and the founder instincts it produced would resurface later in the viral consumer projects that made his name.

A one-click fix that found 150,000 users

Amidst the 2020 COVID-19 pandemic, with so much of work and school suddenly happening over video, Rizzon built a Chrome extension that muted every participant on a Google Meet with a single click, a product that could solve a problem he kept running into himself. The fix was simple, but it turned out plenty of other people had the same complaint.

That became clear fast. Within a year the extension had reached 150,000 users, almost all of them arriving by word of mouth. Its most devoted users were teachers, who were running online classes for 15 to 30 students and had no way to quiet the room without clicking each child one by one. “It was a pain for me, and I just fixed that with an extension,” Rizzon says. “It ended up being useful for a lot of teachers in particular.”

The traction caught the attention of the founder of MP3.com, who emailed Rizzon with an offer to buy it. He sold, marking his first exit and an early sign of the instinct for shipping consumer products that would shape his later work. He has stayed close to open source since, serving as co-founder and core component developer of Zard UI, a shadcn-style component library for Angular developers that has crossed 1,000 stars on GitHub.

The city he engineered to go viral

After years of shipping one project after another, the one that finally broke through was GitCity. The idea came from a post on X about rendering a city, and Rizzon had a first version live within a day. He didn’t write any of it by hand; instead, he built the entire codebase with Claude Code. What it produced was a pixel-art 3D metropolis that renders GitHub developers as buildings, with one structure per coder.

“On the first day, when I had the idea of creating the city, I noticed that this could be a viral product,” he says. “So I prepared and made everything to go viral.”

People took to it immediately. In its first week the city grew from 12,000 buildings to 40,000, and it currently holds more than 80,000. Over two months GitCity drew 180,000 visitors, more than five million social media views, and 5,000 GitHub stars, with roughly 20 people contributing code. Rizzon’s own audience grew alongside it, climbing from 200 Instagram followers to 6,000 and an X account to nearly 4,000.

None of that happened by chance. Rizzon treated distribution as part of the product itself, wiring a one-click “share on X” button into every action a user could take. He also added a feature that lets one building attack another, which fires off an email to the target and pulls them back in to retaliate, and he also opened the experience with a cinematic shot of the skyline and made the 3D rendering run smoothly on phones.

Inspired in part by the indie developer Pieter Levels, he’s also begun earning money from it, taking in $2,000 from sponsored buildings and lining up companies to back a week-long event in which users hunt down a “dark boss” hidden in the city.

The project did more than rack up numbers; it brought recruiters from Delphi, who were looking for someone to carry that same obsession with user experience into their consumer product, and he’s now joining as a product engineer on their San Francisco team. He treats the move less as a destination than as a long apprenticeship, a chance to build a network and learn how the U.S. startup world actually works before starting a company of his own.

More than a developer

Whether the right title is developer, founder, or product engineer, Samuel Rizzon has spent a decade declining to choose just one. The same engineer who built a signature platform now handling more than a billion documents at TOTVS also turned GitCity into a viral calling card, proof that the instinct to ship and the obsession with how a product feels follow him regardless of the label.