How is the screencast recording functionality implemented on scrimba.com?

Question

JavaScript

Came across scrimba. I was interested in where the state of the mouse and text are recorded when creating a screencast.
Turn on any screencast, for example, this one https://scrimba.com/p/pZ45Hz/cyLQNAM by clicking on the play, hear the voice recording, see the cursor movement and write code in real time.
Also, if you make your own screencast, then the current state will be substituted in the track editor with a change in duration.

What is used there besides the monaco editor and how is it implemented at all?
The internal browser, as far as I understand, is an iframe with a link to a deployed page?