This interactive visualization combines a geographic map of countries with a scatter plot of global development indicators. The left panel uses a `d3.geoEqualEarth` projection with `d3.geoPath` to render country polygons, colored blue-white by birth rate. The right panel plots fertility rate against life expectancy using `d3.scaleLinear` for axes and point scaling, with circle size encoding population. Hovering highlights matching regions across both panels via `d3.selectAll` selectors. Data comes from world GEOJSON, world-data-2023.csv, and country-by-continent JSON sources.