This choropleth map colors world countries by economy category using a sequential color scale, with an interactive legend that filters the map by clicking a category. The map renders geographic features with `d3.geoPath` and `d3.geoNaturalEarth1`, while the legend circles respond to clicks to toggle the selected category, dimming non-matching countries. Pan and zoom are enabled via `d3.zoom`. Data comes from the World Atlas TopoJSON and TSV files, processed with TopoJSON’s `feature` method.