     var projection = d3.geoOrthographic()
          .scale(200)
          .translate([250, 250])
          .center([0,0]);

        var geoPath = d3.geoPath().projection(projection);
        var featureSize = d3.extent(countries.features, d => geoPath.area(d));
        var countryColor = d3.scaleQuantize()
          .domain(featureSize).range(colorbrewer.Reds[7]);
        
        d3.select("svg").selectAll("path").data(countries.features)
          .enter()
          .append("path")
            .attr("d",