Ironically, probably just sleepiness - I was posting from bed with an infant that wakes up periodically. Sadly WiFi is not opt-in in my bedroom :-)

It was Finnair from Berlin to Seoul, via Helsinki.

Edit: I found a YouTube video showing a version of this feature from 8 years ago, but I think the one I saw was a bit more refined: https://youtu.be/5-CrsPAZslg - still, interesting that it's this old and I haven't seen it anywhere else.