This choropleth map colors countries by income group using an ordinal color scale with a blue scheme, showing each nation’s classification on a natural Earth projection. The visualization supports zooming and includes a custom color legend with circles and labels. Built with D3 v5, it uses `d3.geoPath` and `d3.geoNaturalEarth1` for map rendering, `d3.zoom` for interaction, and `d3.scaleOrdinal` for color mapping. Data combines TopoJSON world geometry with TSV metadata from the world-atlas package.