random-star.dart

class Star {
  double left;
  double top;
  double extraSize;
  double angle;
  int typeFade;

  Star(
      {@required this.left,
      @required this.top,
      @required this.extraSize,
      @required this.angle,
      @required this.typeFade});
}

// Random star position
for (int i = 0; i < numStars; i++) {
      listStar.add(new Star(
          left: new Random().nextDouble() * screenSize.width,
          top: Random().nextDouble() * screenSize.height,
          extraSize: Random().nextDouble() * 2,
          angle: Random().nextDouble(),
          typeFade: Random().nextInt(4)));
    }

// Render these star
  Widget buildStar(double left, double top, double extraSize, double angle, int typeFade) {
    return new Positioned(
      child: new Container(
        child: new Transform.rotate(
          child: new Opacity(
            child: new Icon(
              Icons.star,
              color: Colors.white,
              size: sizeAnimStar.value + extraSize,
            ),
            opacity: (typeFade == 1)
                ? fadeAnimStar1.value
                : (typeFade == 2) ? fadeAnimStar2.value : (typeFade == 3) ? fadeAnimStar3.value : fadeAnimStar4.value,
          ),
          angle: angle,
        ),
        alignment: FractionalOffset.center,
        width: 10.0,
        height: 10.0,
      ),
      left: left,
      top: top,
    );
  }