This example displays a world map using the Mercator projection, rendered as SVG paths with countries filled in white on a blue ocean background. It loads GeoJSON country boundaries from a gist and uses `d3.geoMercator` for projection, `d3.geoPath` to generate the paths, and `topojson.feature` to convert TopoJSON data. A sphere outline is drawn first, and country paths are appended dynamically from the fetched dataset.