Improve layout on smaller screens

[pinballslouch]

From fjmd1 (Francis Davey ):
@Judgmentals It would be great to add a contact email so I can ask you to remove the annoying white space at the LHS

What's the name of the technique for adding conditionals into your CSS so that the format can change depending on the page width? We can use that to remove the left nav column (which is a bit empty right now anyway) on narrower displays.