HQ Trivia’s founders now have more money to throw into building what has become a viral hit — their live-streaming game-show app played by millions of people, vying to win actual cash.

The startup closed a $15 million round of investment from venture-capital firm Founders Fund, with participation from Lightspeed Venture Partners, which previously invested seed money in the startup. The funding was first reported Tuesday by Axios. The company says the investment gives HQ Trivia (or, technically, parent company Intermedia Labs) a post-money valuation of $100 million.

HQ Trivia quietly launched last August, and now commands audiences of more than 1 million live viewers daily. This past Sunday, more than 2 million people logged in to play the game, which had a prize pot of $50,000 (won by six players, who split the total evenly).

The app’s popularity has turned Scott Rogowsky, the New York stand-up comedian who’s the regular host of the HQ Trivia games, into an internet celeb. He was hired by HQ Trivia through a casting call.

The New York-based startup was founded by Rus Yusupov and Colin Kroll, two of the founders of Vine, the six-second video app acquired by Twitter — which then shut it down four years later.

Yusupov previously told Variety that HQ Trivia hopes to someday bump up cash-prize pool to $1 million per game. HQ Trivia runs the 12-question games weekdays at 3 p.m. and 9 p.m. ET, and on the weekends at 9 p.m. ET. It’s become appointment viewing for the app’s millions of fans.

As far as monetizing the app, HQ Trivia is looking at doing brand integrations or sponsorships, rather than traditional banner or preroll ads, according to Yusupov.

The HQ Trivia questions are created by a team of writers, researchers and fact-checkers, and the trivia gets harder as the game progresses. Players must answer each multiple-choice question within 10 seconds, which makes it tough to launch a Google search for the correct answers.

Founders Fund’s investment in HQ Trivia was led by partner Cyan Banister, who previously had invested in companies including Uber, SpaceX, Postmates, eShares (now called Carta), Affirm and “Pokémon Go” creator Niantic Labs. HQ Trivia plans to use the new funding to grow its staff, including hiring additional engineers, as well as to expand internationally (after recently launching a U.K. version).

“I believe HQ can grow into the next generation-defining entertainment platform,” Banister, who is joining HQ Trivia’s board, said in a statement. “I’m excited to support Rus and Colin as they continue executing on their incredibly ambitious vision for the company.”

As it was out fundraising last fall, HQ Trivia had reportedly been turned down by some VCs who were wary of Kroll’s “alleged bad behavior,” which included “‘creepy’ behavior toward women that made them uncomfortable,” according to a Recode report, citing anonymous sources. Kroll was fired by Twitter in 2014.

In a statement to Axios, Kroll said, “I now realize that there are things I said and did that made some feel unappreciated or uncomfortable. I apologize to those people. Today, I’m committed to building HQ Trivia into a culture-defining product and supporting the dedicated team that makes it all possible.”