This example displays the hierarchical structure of world countries using a tidy tree layout, with continents as branches, subregions as intermediate nodes, and countries as leaf labels. The visualization uses `d3.tree` and `d3.hierarchy` to compute the layout, then renders horizontal links via `d3.linkHorizontal` and text labels within an SVG. Interactive pan and zoom are enabled through `d3.zoom`. The data.json file organizes countries by geographic subregion, and the font size of each label decreases with tree depth.