This example shows how student depression levels relate to their grades using a bar chart and a pie chart. The bar chart visualizes each student's depression level with color-coded bars, while the pie chart displays the distribution of depression levels across the dataset. Both charts use D3 v7's `d3.csv` to load data, `scaleBand` and `scaleLinear` for axes, and `d3.pie` and `d3.arc` for the pie slices. Interactive tooltips appear on hover, and the bar chart uses an event-driven `transition` for the tooltip's opacity changes.