This example displays a world choropleth map coloring countries by their economic income group, with a categorical color legend and zoom/pan functionality. The visualization uses D3 v5 APIs including `geoPath` with `geoNaturalEarth1` projection, `scaleOrdinal` with `schemeSpectral` for color mapping, and `zoom` for interaction. It loads geographic data from the world-atlas TopoJSON and TSV files via `topojson.feature`. Countries render as SVG paths with hover highlighting, and the color legend dynamically generates from the ordinal scale domain.