Last week, Microsoft began mysteriously teasing the first version of Windows on Twitter. Now we know why. It’s just a TV show tie-in.

“Introducing the all-new Windows 1.0, with MS-Dos Executive, Clock, and more!!,” the official Windows account tweeted. It later tweeted about Excel, Chart, and even Flight Simulator,” other Microsoft products from the 1980s. And a lot more.

The account also changed its profile photo to the original Windows 1.0 logo, which indicated that this system only supported tiled application windows, and not floating windows.

And it changed its header photo to another fun Windows 1.0 image.

Clearly, something was going on. I theorized that Microsoft was inspired by my Programming Windows series and was getting nostalgic for the 1980s again. But no. All it is, is a promotional tie-in for the Netflix series Stranger Things, which just launched its third season, set in 1985, the same year that Windows was first released.

And part of that promotion included a new Microsoft Store app for Windows 10 called Windows 1.11.

“With Windows 1.11, experience 1985 nostalgia with a special edition PC app inspired by Windows 1.0 and Stranger Things 3,” the Microsoft Store says of the Windows 1.11 app. “Play games, discover clues and Easter eggs, and unlock secrets and unique Stranger Things 3 content and more. But, beware the Mind Flayer…”

According to the Store, Windows 1.11 is not currently available for some reason. But it was apparently available previously this weekend, so perhaps that is just a temporary glitch. Expect to see it return to the Store on Monday, July 8.

Speaking of glitch, it’s fun that Microsoft is waxing nostalgic, but The Verge claims that the word “Microsoft” is never even uttered once in Stranger Things season 3, nor do any characters use a PC. (I’ve not watched it yet.) Classic.