This example shows a static tree visualization of world countries organized hierarchically by continent and subregion, with all leaf nodes displayed as country names. It uses the D3.js version 6 `tree` layout and `hierarchy` functions to compute the structure from a JSON file, then renders horizontal links with `linkHorizontal` paths in SVG. Text labels are positioned by node coordinates, with font size scaling by depth, and the entire view supports pan and zoom via `d3.zoom`.