content: import 'package:flutter/material.dart';
  import 'package:url_launcher/url_launcher.dart';
  
  class Day49Stack extends StatelessWidget {
    const Day49Stack({Key key}) : super(key: key);
  
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        body: Center(
          /**
           * ? What is Stack....
           * ! Stack is the very important widget....
           * ! With the help of Stack, Tranform, AnimationBuilder we can perform awesome....
           */
          child: Stack(
            fit: StackFit
                .loose, // ! we can give loose(default), expand(fill), passthrough(overlap)....
            alignment: Alignment
                .center, // ! we can give all the alignment here - to modify the root alignment of the child....
            overflow: Overflow.visible, // ! we can give clip, visible....
            children: <Widget>[
              // ! here we add the list of child widgets....
              Container(
                width: 250,
                height: 250,
                color: Colors.red,
              ),
              Container(
                width: 200,
                height: 200,
                color: Colors.green,
              ),
              Container(
                width: 150,
                height: 150,
                color: Colors.yellow,
              ),
              Container(
                width: 100,
                height: 100,
                color: Colors.blue,
              ),
              Container(
                width: 50,
                height: 50,
                color: Colors.black,
              ),
            ],
          ),
        ),
        appBar: AppBar(
          title: Text("Stack"),
          actions: <Widget>[
            IconButton(
              icon: Icon(Icons.help),
              onPressed: () async {
                const url =
                    'https://github.com/sanjaysanju618/100-Days-Of-Flutter-Widgets/' +
                        'blob/master/hundred_days_of_flutter_widget/' +
                        'lib/day049_stack.dart';
                if (await canLaunch(url)) {
                  await launch(url);
                } else {
                  throw 'Could not launch $url';
                }
              },
            )
          ],
        ),
      );
    }
  }
  