This stacked area chart visualizes the average prices of U.S. gasoline, broken down into overall, regular, and midgrade averages, across a weekly timeline. The chart uses a total height to represent the sum of these three averages for each date. Built with D3.js v7, the code computes the averages from the raw data, stacks them using `d3.stack()`, and renders the areas with `d3.area()`. An interactive legend allows users to isolate individual averages by dimming the others, and a tooltip displays precise values via a nearest-date bisector. The data is sourced from the provided CSV file.