Two animated SVG panels show concentric circles whose radii and vertical positions pulse according to sine and cosine functions. Each frame shifts a time parameter, and the number of circles oscillates between 15 and 25. The example demonstrates D3’s data join pattern using `selection.selectAll`, `.data`, and `.join` within a `setInterval` animation loop. The code imports `select` and `range` from D3 v6 and renders the same visualization with black and white fills against contrasting backgrounds.