A multi-line chart displays a week of worldwide temperature readings per city, with each city’s time series drawn as a smooth basis curve. The visualization uses React to render SVG elements, while D3 v5 handles scales, axes, and the `d3.nest()` grouping of data by city. Animated color legend circles appear via a custom `colourLegend` component, and the chart applies a categorical color scale with semi-transparent paths for overlapping lines. Temperature data is loaded from a remote CSV file.