A dark-themed visualization gallery presents two interactive D3 v7 diagrams: a hierarchical tree of programming languages and a force-directed network of authors and papers. The tree uses `d3.hierarchy` and `d3.tree` to arrange nodes by depth, with shapes varying by level and colors by layer, while hover highlights links. The network uses `d3.forceSimulation` with link, charge, and center forces, representing authors as circles and papers as squares, with drag repositioning and tooltips. Both render as SVG with original data.