This choropleth map visualizes countries colored by income group using a natural Earth projection. It loads world geometry from TopoJSON and joins it with TSV metadata via d3.json and d3.tsv, then renders paths with d3.geoPath. A d3.scaleOrdinal with a schemeSpectral range assigns colors, and an interactive legend built with d3-selection shows the categorical scale. The map supports zooming through d3.zoom and highlights countries on hover via CSS.