This choropleth map colors countries by economic classification using a spectral color scale, with an interactive legend that filters map regions by clicking legend items. The visualization combines a world map rendered with d3.geoPath and d3.geoNaturalEarth1, a colorLegend with clickable circles, and d3.zoom for panning and zooming. Country data comes from the world-atlas TopoJSON and TSV datasets, with hover highlighting and tooltips showing country names and values.