This simple bar chart displays nine data values as vertical green bars on an SVG canvas. Each bar responds to mouseover and mouseout events, smoothly transitioning its fill color to blue and back to green using D3 transitions. The visualization is built entirely with D3 v7 APIs, including `scaleBand`, `scaleLinear`, `selectAll`, and `join` to bind data and render rectangles. Axes are omitted, keeping the chart focused on the raw data values, which are also exposed as tooltips via appended `title` elements.