A multi-line chart shows temperature readings from multiple cities over one week, using color-coded paths to distinguish each city. The visualization includes a custom color legend and interactive mouse tracking that displays tooltips with the exact timestamp and temperature at the cursor position. Built with D3 v5, the code uses `scaleTime`, `scaleLinear`, `scaleOrdinal`, `nest`, `line`, and `curveBasis` to structure the data and render SVG paths. The data comes from a CSV file loaded via `csv`, with axes generated using `axisBottom` and `axisLeft`.