I have an updated version of the video "Introduction to Metamath-lamp, part 2":
https://youtu.be/WOp2xQ8mEE4
In this video I've improved the explanation around addition is associative, and also
added a demonstration that metamath-lamp's automation could have found it directly.
Last-minute comments welcome. It's currently unlisted;
I soon plan to switch it to "public".
Part 1 now has the last few useless seconds removed:
https://youtu.be/b-RfoUuQpAQ
and again, I plan to switch this from "unlisted" to "public" soon.
--- David A. Wheeler