This example displays an interactive world map using an equirectangular projection, with countries filled in yellow and hover states shown in gray. The visualization loads geographic boundaries from a TopoJSON file via `d3.json` and converts them to GeoJSON features using the `feature` method from TopoJSON. It renders the map with `d3.geoEquirectangular` and `d3.geoPath`, appending SVG paths for both the Earth sphere and country outlines. A CSS hover rule changes country fill colors without additional JavaScript.