A choropleth map uses a spectral color scale to depict national economies, rendered as SVG paths with D3's geoNaturalEarth1 projection and geoPath. Clicking a color legend tick filters the map by dimming non-matching countries to 10% opacity while highlighting the selected category, and also fades the background sphere. The legend, built with custom colorLegend logic, supports re-clicking to clear the filter. Data joins World Atlas TopoJSON with TSV income and economy metadata via topojson.feature and D3's tsv loader.