This interactive choropleth map displays world countries colored by income group from World Atlas TopoJSON data. Users click legend ticks to filter countries, highlighting selected income categories while dimming others. The map uses d3.geoNaturalEarth1 projection with d3.geoPath for rendering and d3.zoom for pan/zoom controls. A color legend built with d3.scaleOrdinal and schemeSpectral responds to clicks, toggling opacity and stroke width on matching countries.