A choropleth map colors countries by economic classification using an ordinal color scale and the D3 geoNaturalEarth1 projection. Users click legend items to filter the map’s displayed categories, with non-selected legend entries and map countries dimmed to 20% opacity. The visualization relies on d3.geoPath, d3.zoom for panning, and topojson to convert world-atlas TopoJSON data into GeoJSON features.