The Blue Square Challenge

I was originally going to post this as a Stack Overflow question, but I thought reaching out to the dev community with a challenge would be more fun.

The general idea is: if you remove all user agent styles from a webpage, SVGs will stop rendering. Which CSS properties do you need to re-add so they render?

This has led me down an interesting rabbit hole, and I thought this was curious enough to open it up for discussion on HN.