The Concept of a Meta-Font https://www.zigzaganimal.be/elements/the-concept-of-metafont.pdf (beautiful example of making the most of a medium when communicating)
miniblog.
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Fun article on how J manages inverting functions: https://www.adamtornhill.com/articles/jlang/beyondfunctional.html (communicating the exotic ideas of niche PLs is a rare skill!)