Some people baked bread during the pandemic. Some honed their gaming skills. Some even read. Air Mail Pilot practiced not moping. And then there’s 17-year-old Mariella Satow. She has spent the pandemic not only learning American Sign Language (A.S.L.) but also creating an app that provides on-screen signing for movies on Disney+.

That’s a big deal for deaf kids (and adults, too) who can’t read or who have other issues with traditional captions, or who maybe just prefer signing. Mariella’s app, a free Chrome extension called SignUp, launched a month ago and quickly amassed more than a thousand users. “It’s definitely surreal,” she told her local paper, the Sag Harbor Express. “I thought maybe only a dozen people would use it…. It’s just blown up in ways I didn’t think it would.”