text: // TopoJSON data to draw country outlines
  // Source: Natural Earth 1:50m Cultural Vectors, Admin 0 - Countries
  const mapPath = "./naturalEarth50TopoJSON.json";
  
  // 2017 world population data. Source: https://databank.worldbank.org
  
  
  
  /*
  As noted in the second comment, the map data source is Natural Earth. The datasets
  are available to use in the public domain. We used the site mapshaper.org to
  convert shape (`.shp`) and database (`.dbf`) files into a TopoJSON format that
  D3 supports.
  
  The "50" in the TopoJSON name is a reference to the level of detail (1:50m scale)
  and is the middle option. It's a compromise between having enough country
  information (for example, it doesn't cut out smaller Caribbean islands) while
  keeping the file size usable for a web application.
  
  The population numbers you'll show in the map are 2017 data in a comma-separated
  value (CSV) file we downloaded from the World Bank website. It has each country's
  name, population number, and a three-letter country code identifier. This file is
  in the project folder under the name `worldPopulation.csv`.
  
  Using the `const` keyword, create a variable named `popPath`, and set it to the
  path for this population data file as a string.
  */
  
  // Setup
  const svgWidth = 1000;
  const svgHeight = 700;
  
  const svg = d3.select("#map")
      .append("svg")
      .attr("width", svgWidth)
      .attr("height", wvgHeight);
  