Four labeled nodes form a small network of three connected links, rendered in SVG and fully interactive through mouse dragging. The graph uses `d3.forceSimulation` with link, charge, and center forces to position nodes, while a `d3.drag` handler lets users move nodes and update their fixed positions. Elements are drawn with D3 selections, appending `line` and `g` elements whose coordinates are updated on each simulation tick. The code relies on D3 v7's `forceLink` and `forceManyBody` APIs, with text labels placed relative to each node.