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https://asciinema.org/ can do this pretty well too.

If I'm not mistaken, asciinema covers only the second part of the article, i.e., recording. It can't do or control the actual demo.

Full demo can be recorded and edited to add/ remove parts. Also, there is a js player that can be used to provide video player like user interface.

An ASCII enema sounds very uncomfortable.

Never gets old.