Let's make a map with D3.js!
This example shows a world map rendered as an SVG, with countries filled in light green and oceans depicted as a blue sphere. It uses D3.js version 5 and TopoJSON to load and parse world-atlas data, then draws each country with the `d3.geoPath` and `d3.geoNaturalEarth1` projection. The code appends a sphere path first, then fetches the 110m dataset and adds country paths based on the TopoJSON features. Styling is handled via CSS classes.