This interactive choropleth map visualizes world countries colored by economic classification, with a linked legend that filters the map based on selected categories. Clicking a country either selects or deselects it, dimming all other countries; clicking a legend category toggles the map to show only countries in that category. The map uses `d3.geoPath` with the `geoNaturalEarth1` projection, `d3.zoom` for pan and zoom, and `d3.scaleOrdinal` with the spectral scheme for coloring. Data comes from the world-atlas TSV and TopoJSON files, rendered as SVG paths.