This is an interactive bar chart that visualizes the frequency of letters in a dataset loaded from a local CSV file. The chart uses SVG bars with rounded corners and a color gradient, where clicking a bar toggles a selected state that highlights the bar and dims others. Built with React and D3 v7, it uses `scaleBand`, `scaleLinear`, `axisBottom`, and `axisLeft` to create the scales and axes, with a `ResizeObserver` in a custom `useDimensions` hook to make the visualization responsive.