A choropleth map colors world countries by income group, with a categorical color legend and zoom/pan support. Built with D3 v5, it uses `d3.geoNaturalEarth1` and `d3.geoPath` to project TopoJSON world data from the world-atlas package, while `d3.scaleOrdinal` assigns spectral colors. Interactive hovering highlights country borders, and the legend is rendered as an SVG component.