This interactive progress bar shows three workflow stages—Started, In Progress, and Completed—selectable from a dropdown menu. A gray background rectangle fills progressively with color, width, and hue (yellow to orange to green) changing via a 1000-millisecond D3 transition to reflect the chosen state. The code builds the bar using SVG rectangles and the `d3.scale.ordinal` color scale, with the `progressBar()` function controlling state changes and animated updates through `transition().duration()`.