This visualization shows the number of iPhone users from 2007 to 2017, combining a black line chart with a filled area beneath it to emphasize the upward trend. The chart uses D3 v5 APIs including `d3.csv` to load data from a remote GitHub gist, `d3.scaleLinear` for both axes, and `d3.line` and `d3.area` with `curveBasis` to generate the line and area paths. Styling is defined in a separate CSS file, with green tick labels, orange gridlines, and a purple title.