This interactive choropleth map displays global economies color-coded by income group, with a connected color legend that filters the map on click. The map uses D3 v5’s `geoNaturalEarth1` projection, `geoPath`, and `topojson` for world-50m data, while the legend’s ordinal `scaleOrdinal` and `schemeSpectral` drive fills. Hovering highlights countries, and the legend’s click handler toggles opacity, dimming non-selected regions. The SVG rendering supports zoom via D3’s `zoom` behavior.