This interactive tree diagram visualizes the hierarchical structure of world countries, organized by continent and subregion. Using D3.js v5, the visualization employs a horizontal tree layout with SVG rendering. The code leverages D3's `tree`, `hierarchy`, and `linkHorizontal` APIs to compute the layout and generate connecting paths. User interaction is supported through D3's `zoom` event, which applies pan and zoom transformations to the entire group. Text labels display country names, with font size decreasing by depth level, while the data source is a JSON file containing the geographical hierarchy.