This interactive visualization displays a hierarchical tree that expands and collapses when nodes are clicked. The tree uses a horizontal layout with circular nodes and text labels, and collapsible branches animate smoothly via transitions. The code employs D3 v3’s `d3.layout.tree` for positioning and `d3.svg.diagonal` for link paths, with sample data from a manual tree structure containing "Top Level" and dummy child nodes. SVG elements provide the rendering, and animations use `transition().duration()` to update node positions on interaction.