A choropleth map displays world economies by color, showing how countries group by income category. Users hover over color legend items to filter the map, which dims non-matching countries and highlights selected ones. The visualization uses D3 v5 APIs including `geoNaturalEarth1` and `geoPath` for map projection, `zoom` for panning, and `scaleOrdinal` with `schemeSpectral`. It loads geographic boundaries from TopoJSON and economic data from TSV in `loadAndProcessData`. Interactive legend clicks trigger opacity changes through `colorLegend`, with SVG rendering throughout.