This example shows the hierarchical relationships among world countries as a horizontal tree layout. It uses d3.hierarchy and d3.tree to compute node positions, with d3.linkHorizontal generating curved paths for the links. The visualization renders in SVG and supports pan and zoom through d3.zoom. Node labels display country identifiers with font sizes scaled by depth, styled with a Playfair Display font. The data comes from a JSON file loaded via d3.json, and text shadows improve label readability over the teal-colored links.