This visualization displays a tree diagram of world countries nested by continent and region, with each leaf node labeled by country name. It uses the D3 v5 library, specifically `d3.tree` and `d3.hierarchy`, to compute the layout, and `d3.linkHorizontal` to generate the curved link paths. The SVG rendering is styled with teal strokes and serif font text, and includes zoom interaction via `d3.zoom`. Font size scales inversely with tree depth, making top-level regions larger. The example is built around two data files (`data_v1.json` and `data_v2.json`) that structure the hierarchical world geography.