added theme

lib/main.dart

@@ -1,5 +1,7 @@
 import 'package:flutter/material.dart';
 
+import 'theme.dart';
+
 void main() {
   runApp(const MyApp());
 }
@@ -11,11 +13,12 @@ class MyApp extends StatelessWidget {
   Widget build(BuildContext context) {
     return MaterialApp(
       title: 'Flutter Demo',
-      theme: ThemeData(
-        fontFamily: "Ubuntu",
-        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
-        useMaterial3: true,
-      ),
+      theme: lightTheme,
+      darkTheme: darkTheme,
+      home: Scaffold(
+          appBar: AppBar(
+        title: Text('ietn'),
+      )),
     );
   }
 }

lib/theme.dart

@@ -0,0 +1,19 @@
+import 'package:flutter/material.dart';
+
+final _baseTheme = ThemeData(
+  fontFamily: "Ubuntu",
+  useMaterial3: true,
+);
+
+final lightTheme = _baseTheme.copyWith(
+  colorScheme: ColorScheme.fromSeed(
+    seedColor: Colors.deepPurple,
+    brightness: Brightness.light,
+  ),
+);
+
+final darkTheme = _baseTheme.copyWith(
+    colorScheme: ColorScheme.fromSeed(
+  seedColor: Colors.purple.shade100,
+  brightness: Brightness.dark,
+));

pubspec.yaml

@@ -21,23 +21,6 @@ dev_dependencies:
 flutter:
 
   uses-material-design: true
-
-  # To add assets to your application, add an assets section, like this:
-  # assets:
-  #   - images/a_dot_burr.jpeg
-  #   - images/a_dot_ham.jpeg
-
-  # An image asset can refer to one or more resolution-specific "variants", see
-  # https://flutter.dev/assets-and-images/#resolution-aware
-
-  # For details regarding adding assets from package dependencies, see
-  # https://flutter.dev/assets-and-images/#from-packages
-
-  # To add custom fonts to your application, add a fonts section here,
-  # in this "flutter" section. Each entry in this list should have a
-  # "family" key with the font family name, and a "fonts" key with a
-  # list giving the asset and other descriptors for the font. For
-  # example:
   fonts:
     - family: Ubuntu
       fonts: