I used the int data type & experimented with some other data types in Dart. Then, I extracted the home code into a new dart file in the lib folder. At last, I used Scaffold instead of MaterialApp & learned how Scaffold works.

lib > main.dart

import 'package:flutter/material.dart';
import 'home_page.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: HomePage(),
    );
  }
}

lib > home_page.dart

import 'package:flutter/material.dart';

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

  @override
  Widget build(BuildContext context) {

    int days = 30;

    return Scaffold(
        appBar: AppBar(
          title: Text("First Flutter App"),
        ),
        body: Center(
          child: Container(
            child: Text("Hello, welcome to $days days of Flutter!", textDirection: TextDirection.ltr,),
          ),
        ),
      );
  }
}