This example displays an area chart of total insurance charges by age, using data from a CSV file loaded via `d3.csv`. The visualization aggregates charges with `d3.rollups` and `d3.sum`, then renders the result as a smooth area path generated by `d3.area()`, with axes from `d3.axisBottom` and `d3.axisLeft`. The SVG chart includes labeled axes and a title, styled with steelblue strokes and skyblue fills.