World Countries Tree
This example shows a hierarchical tree of world countries, organized by continent and region, where each leaf node represents a country name. The visualization uses a vertical dendrogram layout to display the geographic hierarchy, with all text labels rendered directly in the SVG. The code builds the tree using D3's `tree` and `hierarchy` functions, draws the connecting links with `linkVertical`, and applies D3's `zoom` behavior for interactive panning and scaling. Node labels are sized dynamically based on their depth in the hierarchy.