Valve's one of the greatest video games companies there is. Rich and revered, invested in staff - it's a dream place for any game developer to work at.
That's why people don't leave Valve. Well, most people. Viktor Antonov left Valve, and he was art director for Half-Life 2. He conceptualised City 17, its suburbs and the alien Combine architecture and technology.
So, why did he leave? Until now, he's never really said.
"I left precisely when they stopped making epic, triple-As, which was Half-Life 2," Viktor Antonov told Eurogamer. "Since then, they were episodes.
"Valve is a great place, but I'm interested in projects, not in companies. I went to Valve specifically for Half-Life 2. I went and I collaborated with Arkane to do The Crossing and Dishonored. I put the project above everything else.
"When I went to Valve, they were a small company. They've grown now, they're much bigger, and I'm interested in a certain level of creative risk taking and a certain energy that can be compared to jazz, jamming or rock n' roll, where it's small, it's intense and it's about making revolutions in the media."
Viktor Antonov, creator, Half-Life 2's City 17
"Valve has grown into a much bigger company," he went on, "and what I really enjoy about the philosophy of Arkane is that it's a small, core team that does risky creative projects. And when I went to Valve, they were a small company. They've grown now, they're much bigger, and I'm interested in a certain level of creative risk taking and a certain energy that can be compared to jazz, jamming or rock n' roll, where it's small, it's intense and it's about making revolutions in the media."
Viktor Antonov now works as visual design director for Zenimax - a job that's bigger than his role on this autumn's alluring stealth game Dishonored, which spent an incredible three years in artistic pre-production. His job means he oversees the visual design of all Zenimax-owned studios, which includes Elder Scrolls team Bethesda Game Studios, id Software and Arkane.
Antonov's last work for Valve was pitching Team Fortress 2, he told us. He did that while handing over his position of art director to "a friend" he'd brought in named Moby Francke.
"It causes a lot of surprise that anyone would leave Valve. I left Valve, and all my good friends from there, for the specific reason that I had spent six years of my life on one single project, and that's a lot," Antonov went on to clarify. "And, as an artist, I wanted to express myself in a whole variety of ways. So, since then, I have done two feature films, TV series, I've designed a third feature film, I have done three separate games and an illustrated novel, as an independent author.
"It was very important for me to be independent and active and work with European talent, and have more manoeuvrability in my life."
Moving back to Paris, France, where he'd lived as a young man, was also part of the draw.
Antonov looked back on his time at Valve with admiration.
"I had a very rigorous school training in Art Center College of Design [California] - one of the harshest schools there are. But my best schooling in everything I did today is due to working with Gabe Newell and making Half-Life 2, because this was my second education, pretty much.
"I just moved on," he said.
Would he go back? He admitted to being attracted to projects rather than companies. Does that mean that Valve could twist his arm and tempt him back with Half-Life 3?
"As of today, of course, I work for Zenimax, so technically that would be an inconvenience!" he grinned. "But... A ha...
Arkane art director Sebastien Mitton interjected, joking that Antonov could secretly change his name.
Regaining his composure, Antonov replied: "No, no."
You can see a slideshow of Viktor Antonov's impressive Half-Life 2 artwork on his website.