This example displays a world map with countries filled in green and an ocean-blue background. It uses the `geoEquirectangular` projection from D3 v5, applying `geoPath` to render the geographic shapes, and the `topojson.feature` function to convert data from the world-atlas countries-110m.json TopoJSON file into GeoJSON features. The map is drawn as SVG paths, and countries change to red when hovered.