Frayed nerves. Jittery dispositions. Haggard faces and sunken eyes. As the humans of planet Earth return to work on Monday, we’ll see the same symptoms, country by country. But fear not — this isn’t the start of some global pandemic. It’s simply the understandable after-effect of an opening weekend of World Cup knockout play that delivered enough drama, excitement and emotion to last Earth’s seven billion people for years. See also: Hop on the Bandwagon, America: Your World Cup Team Is Easy to Love We’re just getting started, however, with half the World Cup’s round of 16 still to come, followed by the quarterfinals, semi-finals and July 13 title match. But first, let’s take a moment to consider a truly epic World Cup weekend. We saw one all-time classic match, the continued emergence of a transcendent talent, a controversial, devastating heartbreak and a nation of just 4.8 million people extend its improbable Cinderella run. Here’s everything you need to get up to speed. A true heart-stopper There would be no easing into this World Cup weekend. In Saturday’s opening knockout match, South American upstart Chile, who so unceremoniously dumped defending champ Spain in group play, took host Brazil down to…