This fork visualizes the Keeling Curve, plotting atmospheric CO2 concentration against time from the @curran/keeling-curve-data package. The chart uses D3 scales (scaleTime, scaleLinear) to map the date and CO2 values, with axes, labels, and a filled inner rectangle framing the data. A single line path, generated by d3.line, traces the points, while the viz() function handles all rendering with configurable margins and opacity settings. The example adapts the original chart to support custom data by specifying x and y value accessors.