This area chart visualizes annual cost data from 2000 to 2013. The chart uses a light teal fill with a darker teal stroke to represent the area beneath the line, making the trend in costs over time immediately apparent. The visualization is built with D3.js v6, using `d3.scaleLinear` for both axes, `d3.area` to generate the path, and `d3.extent` for domain calculation. The code includes invisible circles at each data point that reveal a tooltip with the year and cost value on hover, though the example also shows an interactive version with a CSS tooltip and smooth transitions.