Flutter: magic, curved burst

main.dart

// in Burst constructor, children.map(...)
// ...
(particle) => CurvedParticle(
  curve: Interval(
    // Interval would start at random point from 0 to 0.5
    // and finish at random point between 0.6 and 1.0
    Randoms.rnd.nextDouble() * .5,
    Randoms.rnd.nextDouble() * .4 + .6,
  ),
  child: MovingParticle(
    from: Offset.zero,
    to: Randoms.offsetFromSize(size),
    child: particle,
  ),
),
// ...