This example shows a hierarchical tree of world countries organized by continent and subregion, with each country name rendered as text at varying font sizes based on depth. It uses d3.tree and d3.hierarchy to compute the layout from a JSON data file, then renders SVG paths with d3.linkHorizontal for the branches. Zooming and panning are enabled through d3.zoom, and text styling applies a custom Google Font, plus drop-shadow effects via CSS.