This is an opinionated essay about good and bad practices in data visualization. Examples and explanations are below.

Variables are the trickiest part of lambda calculus. And naming is the trickiest part of variables: the most complex code in our lambda evaluator is the part that renames variables to perform capture-avoiding substitutions.
Names are artificial tedious tags whose sole purpose is to aid human comprehension. Can we get rid of them? There ought to be a way to study computation without naming names.

Category Theory Illustrated is a primer in category theory and other mathematical theories that is made to be really accessible to people with no prior exposure to the subject, without being dumbed down, by utilizing visual explanations.

Book about proofs with Lean.

To Mock a Mockingbird and Other Logic Puzzles: Including an Amazing Adventure in Combinatory Logic is a book by the mathematician and logician Raymond Smullyan. It contains many nontrivial recreational puzzles of the sort for which Smullyan is well known. It is also a gentle and humorous introduction to combinatory logic and the associated metamathematics, built on an elaborate ornithological metaphor.

Fourier transforms are a tool used in a whole bunch of different things. This is a explanation of what a Fourier transform does, and some different ways it can be useful.