This example displays the countries of the world as solid red regions with yellow outlines, projected using a natural Earth projection. The map is rendered as SVG paths using D3’s `geoPath` and `geoNaturalEarth1` projection, with geographic data loaded from a world-atlas GeoJSON file. The TopoJSON library’s `feature` function extracts country boundaries from the source data, and each resulting path is appended to the SVG canvas with the country class for styling.