Drupal 8 theming has lots of new features, one of the most exciting is the addition of libraries. You can use libraries to add stylesheets and javascript to your theme, globally or in particular situations.
It's 2015, we are already in the "Mobile Era" and we all love how our modern sites fit and adapt to any screen. It's amazing how a website can stretch to the 52 inches of a Samsung TV and also look good on your mobile phone. But you know what?