From 08dc78bb066694f8d7afbd302532f3e6bd3146d9 Mon Sep 17 00:00:00 2001
From: Matthias Kretschmann <m@kretschmann.io>
Date: Mon, 21 Dec 2015 14:15:26 +0100
Subject: [PATCH] document css unit usage

---
 docs/css.md | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/docs/css.md b/docs/css.md
index cf120d9..d5776f3 100644
--- a/docs/css.md
+++ b/docs/css.md
@@ -1,6 +1,15 @@
 CSS
 ------------------
 
+### Font sizes and units
+
+It's `rem` all the way. The base font size is defined as `px`-based variable and set once the `html` root element. All other font sizes and spacing values are set as `rem` units, being nicely relative to the root font size.
+
+```css
+html { font-size: 18px; }
+p    { font-size: 1rem; }
+```
+
 ### Vendor Prefixes
 
 Just write the official, unprefixed syntax for all CSS 3 features, no need to write the vendor prefixed versions.