Sizing should be `rem` not `em` @base excepted

[pimbrouwers]

Reference: https://webdesign.tutsplus.com/tutorials/comprehensive-guide-when-to-use-em-vs-rem--cms-23984

• Use em units for sizing that should scale depending on the font size of an element other than the root.
• Use rem units for sizing that doesn’t need em units, and that should scale depending on browser font size settings.
• Use rem units unless you’re sure you need em units, including on font sizes.
• Use rem units on media queries