This example presents a choropleth map of world countries colored by economic classification, with an interactive legend that filters the map's display. Clicking a legend category highlights matching countries while dimming others; clicking again clears the filter. The visualization uses D3 v5's `geoNaturalEarth1` projection with `geoPath` for rendering, and `scaleOrdinal` with `schemeSpectral` for color mapping. Pan and zoom are enabled via `d3.zoom`. Geographic data comes from the World Atlas TopoJSON dataset, loaded and processed with `topojson.feature` and merged with TSV metadata.