Moyo: いくつも円を重ねる

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class _MyPainter extends CustomPainter {
  @override
  bool shouldRepaint(_MyPainter oldDelegate) {
    return false;
  }

  @override
  void paint(Canvas canvas, Size size) {
    const double radius = 100;

    final Paint fill = Paint()
      ..color = Colors.black.withAlpha(20)
      ..style = PaintingStyle.fill;
    final Paint stroke = Paint()
      ..color = Colors.black.withAlpha(40)
      ..style = PaintingStyle.stroke
      ..strokeWidth = 1;

    for (int i = 0; i < 360; i += 15) {
      final double rotation = radians(i.toDouble());
      final double x = radius * cos(rotation);
      final double y = radius * sin(rotation);

      canvas.drawCircle(Offset(x, y), radius * 0.7, fill);
      canvas.drawCircle(Offset(x, y), radius * 0.7, stroke);
    }
  }
}