A choropleth map of world countries colored by economic classification allows users to click a country to highlight it while dimming all others, and clicking again deselects it. A linked color legend also supports selection by clicking its swatches. The map uses `d3.geoNaturalEarth1` with `d3.geoPath` to render TopoJSON data from the world-atlas dataset, while `d3.scaleOrdinal` with `schemeSpectral` drives the color scale and `d3.zoom` enables panning and zooming.