This choropleth map visualizes global income groups using a natural Earth projection, with countries colored according to their income classification. The map is rendered as SVG paths generated by `d3.geoPath` from TopoJSON data loaded from World Atlas, combined with TSV metadata. A custom color legend displays the ordinal color scale using `d3.scaleOrdinal` with reds, and a zoom interaction allows viewers to pan and scale the map. Animated transitions with `transition.duration` update the legend circles when the data domain changes.