Let's make a map with D3.js!
This example visualizes world countries on a natural Earth projection, filling landmasses in green against a blue ocean sphere. The code loads geographic data from the world-atlas TopoJSON file, converts it to GeoJSON features using topojson’s `feature` function, and renders each country as a SVG path via `d3.geoPath` with `d3.geoNaturalEarth1`. Styling is applied through CSS classes for the sphere and country fills, with the map auto-sized into a 960×500 viewport.