A world choropleth colors countries by adult literacy rate from a local CSV, joined to country names in the world-atlas TopoJSON topology. The map uses D3's `d3.geoNaturalEarth1` projection with `d3.geoPath` for rendering, and a tooltip appears on hover. Interactive zoom and reset controls use `d3.zoom` with event transforms. Countries are stroked in dark blue and highlighted on hover, with a clickable legend and fit-to-screen button.