He will serve at editor in chief of Periscope, the live video app that Twitter acquired last year and has since made a major focus as the company tries to restart growth amid investor pessimism.

“I still love the written word and Medium, but I honestly can’t think of many things more exciting than helping build a new platform with mobile phones and real time video,” Hansen wrote in an online goodbye letter on Medium, which has tried to be both a service for outside publishers to get their articles online and a source for original writing.

Lately, Medium, created in 2012 by Twitter co-founder Evan Williams as a counter to the 140 character conversations he once encouraged, has seemed to lose interest in creating online articles of its own. Instead, it has been focusing more on its role as a publishing system for others.

Periscope, meanwhile, is looking to encourage higher quality live video streaming after starting as a sort of real-time YouTube for people to show off their skate boarding tricks and grainy concert performances. Increasingly, Periscope is emphasizing more professional quality productions by businesses and celebrities, and has signed a deal to broadcast Thursday night NFL games.

For more about Periscope, watch:

Facebook is also making a push into live video with its Facebook Live while YouTube is said to be working on its own version.

Hansen was previously the editor for Wired magazine’s online arm.