This example demonstrates a custom interaction where hovering over a rectangular plotting area draws crosshair lines from the cursor to the axes, visually linking mouse position to axis values. The visualization uses D3 v7's scaleLinear and axis functions to render labeled X and Y axes around a gray inner rectangle. Mouse movement is tracked via D3's pointer event API, and the code conditionally renders the hover lines only when the cursor stays within the plot boundaries. The project structure modularizes axis rendering into separate files for clear separation of concerns.