This example demonstrates D3’s data join pattern for dynamically updating SVG circles. An animated sine wave controls the number, position, and radius of circles, which are re-bound to the DOM every frame. The module uses `d3.selectAll` with the `.data()` and `.join()` methods to enter, update, and exit elements seamlessly. It also relies on `d3.range` to generate data, and runs via a `setInterval` loop at 60fps.