Kahoot, an online learning platform that lets teachers create and tailor quizzes for their classes, has closed its series A round of funding at $20 million.

The Norwegian startup announced a $10 million raise last September, with notable investors including Microsoft Ventures, Creandum, and Northzone. The company has now added another $10 million to the pot, led by new “private investors,” with its existing investors — including Microsoft Ventures — also participating in the round.

Founded out of Oslo in 2011, Kahoot has emerged as something of a phenomenon in the classroom, recently passing one billion players over its lifespan. It now claims more than 50 million monthly active users and is taking the U.S. by storm.

In a nutshell, Kahoot enables the teacher to play quizmaster with their class, creating and projecting quizzes, or “Kahoots,” onto a whiteboard. Students are able to answer multiple-choice questions on their own devices, on any topic of the teacher’s choosing. There is currently a public library of more than 20 million learning games on the platform.

Above: Challenge from Kahoot

Kahoot has now raised north of $26 million in equity funding, and with its latest cash injection it plans to double down on its product development and expand its “commercial activities,” according to a statement issued by the company.

“We are thrilled to receive this investment from new and existing investors,” said Kahoot CEO Erik Harrell. “We are excited about increasing our investment in our commercial activities and in product development, including in mobile, with mobile being the ubiquitous platform that will enable learning anytime, anywhere among learners of all ages and in all contexts.”

Though Kahoot established itself off the back of its presence in the classroom, the company recently unveiled beta versions of a new mobile app that extends the service into the wider world, with teachers able to send assignments and challenges to kids as homework.

Sign up for Funding Daily: Get the latest news in your inbox every weekday.