This interactive bar chart displays Air Quality Index (AQI) values for three pollutant types (Ozone, PM2.5, and PM10) across each day of the week. The visualization updates dynamically when users click buttons for Monday through Sunday, swapping between seven pre-defined datasets. Built with d3.v4, the code uses `d3.scaleBand` for the x-axis, `d3.scaleLinear` for the y-axis, and a custom `d3.scaleQuantile` color scale with a purple sequential palette. The SVG rendering includes animated transitions when data changes, with button focus states managed through CSS.