The full code , I just want to know what color is under the black cube when or after the user spins the wheel

main.dart

import 'package:flutter/material.dart';

import 'dart:math';

class MyWidget extends StatelessWidget {
  const MyWidget({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Stack(
        alignment: Alignment.center,
        children: [
          Positioned(
            bottom: 40,
            child: Pie(
              onTap: () {},
              onSpin: (p0) {},
            ),
          ),
          Positioned(
            top: 180,
            child: Container(
              width: 30,
              height: 30,
              color: Colors.black,
            ),
          ),
        ],
      ),
    );
  }
}

class Pie extends StatefulWidget {
  const Pie({super.key, required this.onSpin, required this.onTap}); // changed
  final Function() onTap;
  final Function(double) onSpin;
  @override
  PieState createState() => PieState();
}

class PieState extends State<Pie> {
  double finalAngle = 0.0;
  double oldAngle = 0.0;
  double upsetAngle = 0.0;

  @override
  Widget build(BuildContext context) {
    return _defaultApp(context);
  }

  _defaultApp(BuildContext context) {
    return SizedBox(
      width: 300,
      height: 300,
      child: LayoutBuilder(
        builder: (context, constraints) {
          Offset centerOfGestureDetector = Offset(constraints.maxWidth / 2, constraints.maxHeight / 2);
          return GestureDetector(
            behavior: HitTestBehavior.translucent,
            onTap: widget.onTap,
            onPanStart: (details) {
              final touchPositionFromCenter = details.localPosition - centerOfGestureDetector;
              upsetAngle = oldAngle - touchPositionFromCenter.direction;
            },
            onPanEnd: (details) {
              setState(
                () {
                  oldAngle = finalAngle;
                },
              );
            },
            onPanUpdate: (details) {
              final touchPositionFromCenter = details.localPosition - centerOfGestureDetector;

              setState(
                () {
                  finalAngle = touchPositionFromCenter.direction + upsetAngle;
                },
              );

              widget.onSpin(finalAngle);
            },
            child: Transform.rotate(
              angle: finalAngle,
              child: const PieChart(
                data: [30, 30, 30],
                customColours: [Colors.amber, Colors.red, Colors.purple],
                labels: ['a', 'b', 'c'],
                textStyle: TextStyle(),
              ),
            ),
          );
        },
      ),
    );
  }
}

class PieChart extends StatelessWidget {
  final List<double> data;
  final List<String> labels;
  final double angleOffset;
  final double radius;
  final List<Color> customColours;
  final TextStyle textStyle;

  const PieChart({
    super.key,
    required this.data,
    required this.labels,
    required this.customColours,
    required this.textStyle,
    this.angleOffset = 0,
    this.radius = 100,
  });

  @override
  Widget build(BuildContext context) {
    double total = data.fold(0, (previousValue, element) => previousValue + element);
    final startAngle = 0 - pi / 2 + angleOffset;

    return CustomPaint(
      painter: _PieChartPainter(
        data,
        labels,
        total,
        startAngle,
        customColours,
        textStyle,
      ),
      size: Size.fromRadius(radius),
    );
  }
}

class _PieChartPainter extends CustomPainter {
  final List<double> data;
  final List<String> labels;
  final double total;
  final double startAngle;
  final List<Color> customColours;
  final TextStyle textStyle;

  _PieChartPainter(
    this.data,
    this.labels,
    this.total,
    this.startAngle,
    this.customColours,
    this.textStyle,
  );

  @override
  void paint(Canvas canvas, Size size) {
    final center = Offset(size.width / 2, size.height / 2);
    final radius = min(size.width, size.height) / 2;
    final rect = Rect.fromCircle(center: center, radius: radius);
    final paint = Paint()..style = PaintingStyle.fill;

    double sweepAngle = 0;

    for (int i = 0; i < data.length; i++) {
      final ratio = data[i] / total;
      final sweepRad = ratio * 2 * pi;

      paint.color = _getColor(i);

      canvas.drawArc(rect, startAngle + sweepAngle, sweepRad, true, paint);

      final labelAngle = startAngle + sweepAngle + sweepRad / 2;
      final labelX = center.dx + (radius * 0.6) * cos(labelAngle);
      final labelY = center.dy + (radius * 0.6) * sin(labelAngle);
      final labelOffset = Offset(labelX, labelY);

      _drawLabel(canvas, labels[i], labelOffset);

      sweepAngle += sweepRad;
    }
  }

  void _drawLabel(Canvas canvas, String label, Offset offset) {
    final textSpan = TextSpan(
      text: label,
      style: textStyle,
    );

    final textPainter = TextPainter(
      text: textSpan,
      textDirection: TextDirection.ltr,
    );

    textPainter.layout();
    final textOffset = Offset(offset.dx - textPainter.width / 2, offset.dy - textPainter.height / 2);

    textPainter.paint(canvas, textOffset);
  }

  Color _getColor(int index) {
    return customColours[index % customColours.length];
  }

  @override
  bool shouldRepaint(_PieChartPainter oldDelegate) {
    return oldDelegate.data != data ||
        oldDelegate.labels != labels ||
        oldDelegate.total != total ||
        oldDelegate.startAngle != startAngle;
  }
}

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyWidget(),
    );
  }
}