This example shows a hierarchical tree visualization of world countries, organized by continent and subregion as a branching structure. The graph renders country names as text labels with size decreasing by depth, connected by curved links. Built with D3 v5, it uses `d3.hierarchy`, `d3.tree`, and `d3.linkHorizontal` to compute and draw the layout, with `d3.zoom` enabling pan and zoom on the SVG. Data comes from a local `data.json` file.