Building the UI of the app

The first step toward creating the game is to build the basic components of the UI. After creating a new app, we'll build a ball, a bat, and a text for the score:

1. Let's create a new app, which we can call simple_pong.
2. In the main.dart file, in the build() method of the MyApp stateless widget, we'll return a MaterialApp, whose title is "Pong Demo", and, for the theme, we'll use the classic blue as primarySwatch.
3. In the home of MaterialApp, we'll place a scaffold whose AppBar will take a text containing "Simple Pong".
4. In the body, we'll place an empty container for now, but we will fix that later on.

You can see the steps listed in the following code:

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
   @override
   Widget build(BuildContext...