A force-directed graph shows the network structure of nodes and links, with each node colored by group and links weighted by value. Clicking a node highlights all connected links in red and simultaneously highlights the corresponding row and column in an adjacent adjacency matrix, where cell opacity reflects link weight. The implementation uses `d3.forceSimulation` with `forceLink`, `forceManyBody`, and `forceCenter`, renders nodes as SVG circles with drag and zoom support, and loads data from a `.edges` file.