> I think that textbooks, math textbooks in particular, are an example where print publishing does a disservice. (I'm counting PDFs here too.) By having to lay

> I think that textbooks, math textbooks in particular, are an example where print publishing does a disservice. (I'm counting PDFs here too.) By having to lay everything out in print form, you have to clutter up your explanations with examples and footnotes that take up physical room. Here, the examples are toggle-able. If I _want_ to explore an example, I can. But I don't need to. This kind of thing is especially helpful when reviewing content for, say, a test rather than learning it for the first time. This sounds so much like a meeting of Lamport's idea of how to structure a proof (https://lamport.azurewebsites.net/pubs/proof.pdf https://lamport.azurewebsites.net/pubs/proof.pdf) and the Stacks project (https://stacks.math.columbia.edu https://stacks.math.columbia.edu).