This example visualizes air quality patterns, comparing SO2, particle, and NO3 concentrations across 31 U.S. states from 2008 to 2018 through animated line charts. Users select a pollutant via radio buttons, triggering an animation that reveals trends over time. The visualization uses D3.js v4 with SVG rendering, featuring a custom color palette for state-specific lines. The code integrates React for structure and employs D3’s data join and transition methods to update the chart dynamically, with data embedded directly in the script.