This fork of D3's tree diagram displays a hierarchical breakdown of world countries, organized by continent and subregion, with all terminal nodes labeled in a serif font. The visualization is rendered as an SVG, with nodes positioned horizontally based on depth. The code uses D3 v5’s `tree` layout, `hierarchy` and `linkHorizontal` helpers to compute paths, and a `zoom` interaction that rescales the entire drawing on user input. Text size scales inversely with depth, and link paths are styled with a teal stroke.