A choropleth map colors countries by economic classification using an ordinal color scale. Clicking a legend entry filters the map, dimming non-matching countries while highlighting the selected category. The visualization uses d3.geoNaturalEarth1, d3.geoPath, and d3.zoom for pan and zoom, with d3.scaleOrdinal and schemeSpectral for coloring. Data comes from the World Atlas TopoJSON and TSV files loaded via d3.json and d3.tsv, rendered as SVG with clickable legend ticks.