[molticrystal]

> with no commentary or explanation.

Enable subtitles/closed captioning to see additional commentary provided by him about what is happening.

>the video is someone speed-typing the source code

They are not actually typing it at all, from the faq https://bisqwit.iki.fi/jutut/kuvat/programming_examples/nese...

  Q) Is the video sped up? Or, is that your real typing speed?
  A) No, it's not sped up. But the input is pre-choreographed. The computer
     implements the choreography, as well as designs a part of it.
     It is a TAS, except I'm not speedrunning; I'm just aiming for
     15 minutes and to utilize it in the most entertaining manner.
     My typing speed is not the focus of that video; it is not even
     being presented except in a small part of the 2/2 video.
     The focus is in the source code.

He actually wrote his own editor that he uses in the video and I believe that assists with the choreography.

[stavros]

Yes, my point wasn't at all about the speed. You can replace "speed-typing" with "displaying at a speed too high to read, much less think about".