Calculus made easy

https://calculusmadeeasy.org/
https://github.com/nadvornix/calculus-made-easy

Calculus Made Easy is a book on calculus originally published in 1910 by Silvanus P. Thompson, considered a classic and elegant introduction to the subject.

I read "Calculus Made Easy" by Silvanus P. Thompson and it's still to this day my inspiration for explaining complex technical topics to lay people. It's a fantastic book, and even if you know math you must read it if you want to understand how to teach complexity to others. (source)

via news.yc