This example demonstrates a force-directed graph layout with nodes grouped into nested clusters. The visualization uses WebCola's `cola.d3adaptor` to position seven labeled rectangles connected by eight links, while translucent background rectangles represent the hierarchical group structure. Nodes can be dragged to reposition, and double-clicking releases a node, allowing it to move freely again. The data comes from `graph.json`, which specifies node sizes, link connectivity, and a group hierarchy, and the SVG rendering is updated during each simulation tick.