A hierarchical tree visualization displays the world’s countries, organized by continent and then by subregion (e.g., Southern Asia, Western Asia). Node labels use the `Playfair Display` serif font, with font size decreasing by tree depth. The chart is rendered as an SVG using `d3.tree`, `d3.hierarchy`, `d3.linkHorizontal`, and `d3.zoom`. It loads `data.json` and uses `root.descendants()` to place text labels and generate paths for the links between nodes.