[101101001010]

My guess would be that it was created in Bookdown with the Tufte handout style[0]

[0] https://bookdown.org/yihui/rmarkdown/tufte-handouts.html

[dfc]

It looks like the author used pandoc with Tufte handout

* css: https://github.com/edwardtufte/et-book/

* latex: tufte-handout style from CTAN