This choropleth map colors countries by income group using a diverging red-blue ordinal scale, with a zoomable Natural Earth projection and a color legend built from custom SVG circles. The visualization loads world country boundaries from TopoJSON and joins them to TSV metadata, then renders each nation as a styled SVG path with hover highlighting. It uses d3.geoPath, d3.geoNaturalEarth1, d3.zoom, and d3.scaleOrdinal with the schemeRdBu palette, while the legend is implemented as a reusable module.