An interactive scatter plot displays the relationship between Microsoft and Walmart stock returns. Users click and drag to draw their own estimated regression line onto the chart. A button reveals the actual least squares fit, computed using the `d3-regression` library’s `regressionLinear()` function. Data points render as circles from the CSV file, while the user’s line is drawn with `d3.drag()` pointer events. The SVG visualization uses D3 v6 scales, axes, and `transition`-less direct attribute updates.