An area chart displays battery life versus screen size across phone categories. The chart uses semi-transparent, color-coded areas for each category, which are differentiated by a legend. Data is loaded from a CSV file using `d3.csv` and rendered as SVG with D3 v7. The visualization uses `d3.scaleLinear` for axes, `d3.scaleOrdinal` with `d3.schemeTableau10` for colors, and `d3.area` with `d3.curveMonotoneX` to create smooth, filled areas for each category.