Fifteen circles appear one by one every second, with each new circle positioned along a sine wave based on its index. Built with D3 v3 and rendered as SVG, this example demonstrates the `selectAll` data-join pattern, where `range(15)` generates the dataset and `enter().append()` adds new circle elements. The animation updates the wave at a fixed interval, showing a static wave shape that shifts position with each tick due to changing sine values.