This choropleth map visualizes global income groups, with countries colored according to a categorical scale. Users can click legend items to filter the map, dimming countries that do not match the selected category. The visualization is built with D3.js v5, using `geoNaturalEarth1` and `geoPath` for map projections and SVG paths for rendering. Data is loaded from the World Atlas TopoJSON and TSV datasets, with the color legend implemented as an interactive SVG component.