A choropleth map colors countries by economic classification using a spectral color scale, with an interactive legend that filters the map when clicked. Hovering over a legend item dims all countries except those matching the selected category, while clicking toggles the filter on and off. Built with D3 v5, the visualization uses `d3.geoNaturalEarth1` for projection, `d3.geoPath` for rendering SVG paths, and `d3.zoom` for panning and zooming. Geographic data comes from the World Atlas TopoJSON dataset, with country names and economic groups loaded from a TSV file.