This visualization shows BMW car sales volumes aggregated by year from an external CSV dataset, displaying a line chart with circular data points. The code uses D3 v7 with an SVG rendering approach, applying `d3.csv` for data loading, `d3.rollup` for aggregation, and `d3.line` to generate the orange line path. Interactive tooltips appear on mouseover using DOM events and a styled div, while grid lines and axes are created with `d3.axisLeft` and `d3.axisBottom`. The implementation includes linear scales for positioning and an animation showcase via transitions on tooltips.