This dark-themed line chart visualizes monthly sales data from January 2023 through December 2024, sourced from a CSV file. Built with D3 v7, the reusable `lineChart()` function renders an SVG path using `d3.line()` with `curveMonotoneX`, along with circles for data points. Interactive tooltips appear on mouse hover via D3 event handlers. The chart includes a programmatic `update()` method that animates transitions for axes and the line when new data is provided.