This example displays a world map with countries colored blue and outlined in black, rendered using the Natural Earth projection. Hovering over a country turns it red, providing visual feedback. The map uses D3’s `geoPath` with a `geoNaturalEarth1` projection, loading country boundaries as TopoJSON and names from a TSV file. A CSS `:hover` rule triggers the color change, and a `<title>` element shows the country name on hover.