Widget Container

main.dart

import 'package:flutter/material.dart';

void main() => runApp(App());

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomePage(),
    );
  }
}

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Flutter Demo')),
      body: Container(
        width: 200.0,
        height: 200.0,
        margin: EdgeInsets.only(
          left: 24.0,
          top: 24.0,
        ),
        padding: EdgeInsets.only(
          left: 24.0,
          top: 24.0,
        ),
        decoration: BoxDecoration(
          color: Colors.teal,
          borderRadius: BorderRadius.only(
            topRight: Radius.circular(24.0),
            bottomLeft: Radius.circular(24.0),
          ),
        ),
        child: Text('HELLO WORLD'),
      ),
    );
  }
}