A choropleth map colors countries by economic classification, sourced from the World Atlas dataset and displayed using the Natural Earth projection. Clicking a color swatch in the legend filters the map, dimming all countries except those matching the selected category, while a highlighted stroke marks the active group. Built with D3 v6, it uses `d3.geoPath` for map geometry, `d3.scaleOrdinal` with the spectral scheme for color mapping, and `d3.zoom` for interactive panning and zooming. Hovering a country reveals its name and value via a tooltip.