main.dart

import 'package:flutter/material.dart';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: MyWidget(),
        ),
      ),
    );
  }
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Stack(
  alignment: Alignment.center,
  children: [
    CustomPaint(
      size: Size(100, 100),
      painter: BackgroundPainter(),
    ),
    Container(
      width: 90, height: 90,
      decoration: BoxDecoration(
        shape: BoxShape.circle,
      ),
      child: Material(
        color: Colors.green,
        child: InkWell(
          onTap: () {},
          child: Container(
            child: Icon(Icons.ac_unit),
          ),
        ),
      ),
    ),
  ],
);
  }
}

class BackgroundPainter extends CustomPainter {
   @override
  void paint(Canvas canvas, Size size) {
    Paint paint = Paint()
      ..color = Colors.red
    ..style = PaintingStyle.fill;
    
    Path path = Path()
      ..moveTo(0,0)
      ..lineTo(size.width, 0)
      ..lineTo(size.width, size.height)
      ..lineTo(0, size.height)
      ..close();
      
    canvas.drawPath(path, paint);
  }
  
  @override
  bool shouldRepaint(covariant CustomPainter oldDelegate) {
    return true;
  }
}