This area chart shows the average vehicle price by year, with a green shaded region rising and falling across the time series. The visualization uses D3.js to load CSV data from a GitHub gist, aggregate prices per year with `d3.rollup`, and render the area using `d3.area()` with a monotone curve. Axes, gridlines, and labels are created via D3’s axis APIs, while the SVG output is styled with CSS for a clean presentation.