Three cities' daily temperatures are shown as smooth, colored lines over a shared time axis, demonstrating brushing and zooming interactivity in D3. Users can click a city to toggle its line's visibility, hover to highlight a specific line while dimming others, and zoom with the mouse to inspect date ranges. The visualization uses d3.zoom with `rescaleX` to update the x-axis and line geometry, while d3.line with `curveBasis` creates the smoothed paths. Data is loaded from a TSV file and rendered as SVG, with d3.scaleOrdinal assigning categorical colors.