This example visualizes the World Bank’s country-level economy classifications on a choropleth map. Users can select a specific economy class from the color legend, which highlights matching countries and dims all others, while hovering over a country reveals its name and economic category. Built with d3.js v5, the map uses the `geoMercator` projection and `geoPath` to render country shapes from TopoJSON data. The legend, implemented with `scaleOrdinal` and `schemeSpectral`, enables interactive filtering through mouse clicks.