A dynamic animation shows fifteen circles moving in a sine-wave pattern across the screen, with their radii oscillating over time. The example uses D3 v7’s `select`, `range`, and data joins (`join`) to bind and update SVG circle elements every frame, driven by `setInterval` at roughly 60fps. A static green rectangle anchors the composition, while circle positions and sizes are computed from a time variable `t`, demonstrating basic D3 transitions and SVG rendering without external data sources.