D3 Transitions
This animation demonstrates D3’s transition system by staging six colored circles that grow from a radius of zero to their target sizes, with each circle entering on a staggered 200-millisecond delay. After the initial enter transition, the circles remain static; the code uses `d3.selectAll` to bind data by `id`, then applies `d3.transition` with `.duration(2000)`, `.delay`, and `.attr` tweening to animate the `r` attribute. The example uses D3 v7 and relies on the `select`, `transition`, and `easeLinear` imports, with a light green SVG background and hardcoded circle positions and fills.