A choropleth map of world countries colored by economy, with an interactive color legend that filters the map to highlight countries in a selected category. Clicking a legend entry dims non-matching countries and increases their stroke width; clicking again clears the filter. Built with D3 v5, the visualization uses `d3.geoNaturalEarth1` and `d3.geoPath` to render topojson country features from the world-atlas dataset, with `d3.scaleOrdinal` and `schemeSpectral` for colors.