This example pairs a world map with a bar chart to explore military spending by country in 2018. The map uses `d3.geoEqualEarth` and `d3.geoPath` to render countries, colored via a linear scale from red to blue based on spending, while the adjacent bar chart filters to nations spending over $200 billion. Both visualizations respond to mouseover and mouseleave events, highlighting matching countries and bars. Data comes from a GeoJSON world map and a CSV of military spending, processed with `d3.json` and `d3.csv` under D3 v6.