This area chart visualizes total sales over time, with a semi-transparent steelblue fill beneath a blue line. The chart is built using D3 version 7, loaded from the d3js.org CDN, and rendered as an SVG element with a white background and shadow. The JavaScript file `areaChart.js` draws the area and line paths using D3’s scalable vector graphics APIs, while axis labels are styled with CSS classes. The data source is not specified in the provided code, but the chart’s layout and styling are defined in the HTML and CSS files. The visualization uses D3's standard `svg.path` and `svg.line` elements to encode the trend.