This example demonstrates a generative, interactive line chart within a black canvas. As a timer progresses, the visualization automatically appends points to a path, creating a random walk from the bottom of the screen upward. A semi-transparent radial gradient follows the user's mouse cursor, acting as a spotlight that reveals the chart's details. The implementation relies on D3 v7's selection and `.join()` operations to efficiently manage SVG elements, with mouse events updating a circle and text label in real time.