This choropleth map colors countries by income group using an ordinal color scale with a spectral scheme. The visualization loads world geometry from TopoJSON and joins it with TSV metadata, then renders the map with a natural Earth projection via d3.geoPath. Users can pan and zoom through d3.zoom, while a custom color legend built with SVG circles and text shows the categorical mapping. Hovering over a country highlights it in red and reveals its name and income group in a tooltip.