This example demonstrates the enter-update-exit cycle in D3 data joins. An animated sine wave drives a set of circles across the screen, where the number of circles changes dynamically based on the oscillation, and each circle’s position and radius fluctuate over time. The visualization combines `d3.select`, `selection.data`, and `selection.join` from D3 v7 to bind data to SVG elements, with a `setInterval` loop updating the visualization at 60 frames per second. The data is generated procedurally using `d3.range` in the `makeData` function.