This example shows a hierarchical tree of world countries organized by continent and subregion. The layout uses D3’s `tree()` and `hierarchy()` functions to compute node positions, with curved `linkHorizontal()` paths connecting parent and child nodes. Labels display each country’s full name, with font size decreasing by tree depth. The visualization supports pan and zoom through D3’s `zoom()` behavior, applied to a group element. Data comes from a static `data.json` file, and all rendering is done with SVG elements styled via external CSS.