This example shows a letter frequency bar chart with earnings and view counts from a fictional data CSV. The chart visualizes counts across letters, with bars that highlight when clicked. Built with React and D3 v7, it uses `scaleBand` and `scaleLinear` for positioning, `axisBottom` and `axisLeft` for axes, and `ResizeObserver` to adapt to container size. Clicking a bar toggles its selection, changing fill color and opacity.