A choropleth map of global economies uses ordinal color encoding, with a legend that lets users click color swatches to filter countries by economic group. Non-matching countries dim to low opacity, and the selected legend item highlights its corresponding category on the map. The visualization is built with D3 v5, using `d3.geoPath` and `geoNaturalEarth1` for map projection, `scaleOrdinal` with `schemeSpectral` for colors, and `zoom` for panning. Data comes from TopoJSON world-atlas files, with SVG rendering for all elements.