A hierarchical tree diagram maps countries grouped by continent and subregion, using a D3.js v5 layout with horizontal link paths. The visualization reads country names from a local `data.json` file, displaying text labels sized inversely to their depth in the tree. Built with the `d3.tree`, `d3.hierarchy`, and `d3.linkHorizontal` APIs, it supports interactive zooming via a custom `zoom` event that applies SVG transforms.