This interactive tree visualization displays the hierarchical structure of world countries, organized by continent and subregion. Built with D3 v5, it renders an SVG that responds to the browser window size, using `d3.json` to load the nested geographic data. The layout applies `d3.forceSimulation` to position the nodes. The code draws a rounded rectangle background and constructs a hierarchical tree diagram, with each node labeled by its corresponding country or region name from the source dataset.