A single rounded bar chart compares total monthly expense against budget, encoding the ratio as bar width. The bar animates from zero width to its final proportional length using a D3 v4 `transition`, with its fill color shifting from teal to orange to red as the ratio exceeds thresholds. Text labels display the fixed expense amount, while an SVG input element permits budget adjustment. The visualization renders with D3 selections, a linear scale for width mapping, and SVG rectangle and text elements.