Good initiative @djinn

I wish there is enough support for this so that this effort of love (rage is an extreme form of love!) is useful for young learners. ref

Can you point us to the original sources for explanation please?
There is some explanation and similar code at
https://beautifulracket.com/basic-2/
https://beautifulracket.com/basic-2/better-line-errors.html
https://beautifulracket.com/basic-2/source-listing.html

Could you figure out their license ?
https://beautifulracket.com/#this-book-is-not-free
https://beautifulracket.com/why-you-should-pay.html