This is a wonderful idea and execution.

Tip for people trying this out, to experience it fully you have to:

- login with github - edit some text - then hit play again. The preview will then update.

- also, you can record your own edits to the video.

I am surprised by the quality and thoughtful demos.

Some simple things would make it better, like updating automatically without hitting play. Also, I think the videos should have x buttons to close them, not just clicking in another area.