Six circles, initially red and arranged horizontally, demonstrate the D3 enter, update, and exit lifecycle. The animation updates the data array and re-renders: after two seconds, one circle is removed via `exit().remove()`, and after four seconds, the first circle updates from type 'A' to 'B', changing its fill color through a 2-second `transition()`. The SVG renderer uses `d3.scaleOrdinal` for color mapping.