This choropleth map colors countries by income group using an ordinal color scale with the spectral scheme. It renders geographic boundaries with d3.geoPath and a Natural Earth projection, using TopoJSON data from the world-atlas package. Hovering highlights countries in red, while a legend built with custom D3 code displays the color categories. The map supports zooming and panning through d3.zoom, and tooltips show each country’s name and income group.