This example shows a zoomable world map built with React and D3 v5, where hovering over a country highlights it in red and displays its name as a tooltip. The map renders SVG paths using `d3.geoPath` and a Mercator projection, with geographic data loaded from the world-atlas TopoJSON and country names matched via TSV. Interaction includes a `d3.zoom` handler that transforms a group element containing all country paths, and CSS `:hover` rules change fill color. The code demonstrates combining TopoJSON feature extraction, data joins, and simple event-driven styling.