This example shows an interactive choropleth map where clicking a legend category highlights matching countries and dims all others. Built with D3 v5 using `d3.geoMercator` and `d3.geoPath` for SVG rendering, it also applies `d3.zoom` for panning. The legend uses `d3.scaleOrdinal` with `schemeSpectral`, and click events toggle the selected category. Data comes from the World Atlas TopoJSON and TSV files, loaded via `Promise.all`.