Like Amazon, Airbnb, and many other startup breakthrough stories, Whatnot traces its origins back to a small rental home. But unlike other founder success stories, one of its creators took a rather radical approach to productivity: total seclusion.

Co-founder Logan Head “locked himself in his room for about four or five weeks to build it,” Whatnot CEO Grant LaFontaine told Fortune’s Allie Garfinkle on a recent episode of the Term Sheet vodcast. “He was coding 16 hours a day, six days a week.”

Inspired by their own collectibles habits, LaFontaine and Logan Head launched their livestream shopping app in December 2019, and applied to join Paul Graham’s Y Combinator three months later for the program’s winter cohort. The app has become the largest livestream shopping platform outside of Asia, offering an interactive format where sellers display items for sale via livestream, allowing customers to bid for and ask questions about the products. Whatnot, which has grown into America’s largest livestream shopping app, had one major challenge: hosting its first livestream auction.

“He came out and he’s like, ‘All right, I’m done. We got to test this,’” LaFontaine recalled of the “mentally exhausting” daily grind. “He was just really nervous that it wasn’t going to work.”