这跟他们的前辈在原生应用程序或印刷出版物中做的设计或多或少有点类似。

CSS3 - 知乎 https://www.zhihu.com/topic/19562598/hot

Jeremy Church:

While em is relative to the font-size of its direct or nearest parent,rem is only relative to the html (root) font-size.

Jeremy tends to favor em, because of the ability to control an area of a design. As in, scale the type in that specific area relatively. I have tended to like rem because of the ability to scale type across the entire page easily, but I've gotten into issues where that wasn't good enough control so I could see moving back to em for that reason.

Confused About REM and EM? | CSS-Tricks https://css-tricks.com/confused-rem-em/

There’s more to the CSS rem unit than font sizing | CSS-Tricks https://css-tricks.com/theres-more-to-the-css-rem-unit-than-font-sizing/

 Font sizing with rem - Snook.ca https://snook.ca/archives/html_and_css/font-size-with-rem