Here are the two hover styles. Which one do we want to adopt as the standard?
MediaWiki UI:
box-shadow: 0 1px rgba(0, 0, 0, 10%), inset 0 -3px rgba(0, 0, 0, 20%);
OOjs UI:
box-shadow: 0 0.1em 0 0 rgba(0, 0, 0, 0.2), inset 0 -0.2em 0 0 rgba(0, 0, 0, 0.2);