diff --git a/android/app/build.gradle b/android/app/build.gradle
index caaf1ed..525c66c 100644
--- a/android/app/build.gradle
+++ b/android/app/build.gradle
@@ -26,7 +26,7 @@ apply plugin: 'kotlin-android'
 apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
 
 android {
-    compileSdkVersion 30
+    compileSdkVersion 31
 
     compileOptions {
         sourceCompatibility JavaVersion.VERSION_1_8
@@ -45,7 +45,7 @@ android {
         // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
         applicationId "com.example.flip_card_game"
         minSdkVersion 16
-        targetSdkVersion 30
+        targetSdkVersion 31
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
     }
diff --git a/android/app/src/main/AndroidManifest.xml b/android/app/src/main/AndroidManifest.xml
index f36942e..b4fa2ff 100644
--- a/android/app/src/main/AndroidManifest.xml
+++ b/android/app/src/main/AndroidManifest.xml
@@ -9,7 +9,8 @@
             android:theme="@style/LaunchTheme"
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
             android:hardwareAccelerated="true"
-            android:windowSoftInputMode="adjustResize">
+            android:windowSoftInputMode="adjustResize"
+            android:exported="true">
             <!-- Specifies an Android theme to apply to this Activity as soon as
                  the Android process has started. This theme is visible to the user
                  while the Flutter UI initializes. After that, this theme continues
diff --git a/android/build.gradle b/android/build.gradle
index ed45c65..b622d73 100644
--- a/android/build.gradle
+++ b/android/build.gradle
@@ -1,12 +1,12 @@
 buildscript {
-    ext.kotlin_version = '1.3.50'
+    ext.kotlin_version = '1.7.20'
     repositories {
         google()
         mavenCentral()
     }
 
     dependencies {
-        classpath 'com.android.tools.build:gradle:4.1.0'
+        classpath 'com.android.tools.build:gradle:7.1.2'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
 }
diff --git a/android/gradle/wrapper/gradle-wrapper.properties b/android/gradle/wrapper/gradle-wrapper.properties
index bc6a58a..595fb86 100644
--- a/android/gradle/wrapper/gradle-wrapper.properties
+++ b/android/gradle/wrapper/gradle-wrapper.properties
@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.7-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.2-all.zip
diff --git a/lib/flip_card_core.dart b/lib/flip_card_core.dart
new file mode 100644
index 0000000..8d4ea95
--- /dev/null
+++ b/lib/flip_card_core.dart
@@ -0,0 +1,65 @@
+import 'dart:async';
+
+import 'asset_name.dart';
+
+class FlipCardCore {
+  final _imageNames = [
+    AssetImageName.orange,
+    AssetImageName.banana,
+    AssetImageName.apple,
+    AssetImageName.strawberry,
+  ];
+
+  final List<String> _randomImageNames = [];
+  int _frontCardCount = 0;
+  final List<int> _frontCardIndexes = [];
+
+  final StreamController toggleCardToFrontStream = StreamController();
+  final StreamController cardsMatchedStream = StreamController();
+
+  List<String> getRandomCardImages() {
+    return _randomImageNames.map((e) => e).toList();
+  }
+
+  void reset() {
+    // add 2 times
+    _randomImageNames.clear();
+    _randomImageNames.addAll(_imageNames);
+    _randomImageNames.addAll(_imageNames);
+
+    // shuffle
+    _randomImageNames.shuffle();
+  }
+
+  void flipCard(int cardIndex) {
+    _frontCardCount++;
+    _frontCardIndexes.add(cardIndex);
+  }
+
+  void checkCards() {
+    print('_frontCardCount : $_frontCardCount');
+    print('_frontCardIndexes : $_frontCardIndexes');
+
+    if (_frontCardCount == 2) {
+      toggleCardToFrontStream.add(true);
+      if (_frontCardIndexes.length >= 2) {
+        String firstCardName = _randomImageNames[_frontCardIndexes[0]];
+        String secondCardName = _randomImageNames[_frontCardIndexes[1]];
+        if (firstCardName == secondCardName) {
+          _randomImageNames[_frontCardIndexes[0]] = '';
+          _randomImageNames[_frontCardIndexes[1]] = '';
+
+          cardsMatchedStream.add(true);
+        }
+      }
+
+      _frontCardIndexes.clear();
+      _frontCardCount = 0;
+    }
+  }
+
+  void dispose() {
+    toggleCardToFrontStream.close();
+    cardsMatchedStream.close();
+  }
+}
diff --git a/lib/main.dart b/lib/main.dart
index 472741d..8f9f698 100644
--- a/lib/main.dart
+++ b/lib/main.dart
@@ -1,5 +1,5 @@
 import 'package:flip_card/flip_card.dart';
-import 'package:flip_card_game/asset_name.dart';
+import 'package:flip_card_game/flip_card_core.dart';
 import 'package:flutter/material.dart';
 
 void main() {
@@ -31,37 +31,29 @@ class MyHomePage extends StatefulWidget {
 }
 
 class _MyHomePageState extends State<MyHomePage> {
-  final _imageNames = [
-    AssetImageName.orange,
-    AssetImageName.banana,
-    AssetImageName.apple,
-    AssetImageName.strawberry,
-  ];
-
-  final List<String> _randomImageNames = [];
+  final FlipCardCore _flipCardCore = FlipCardCore();
   final List<GlobalKey<FlipCardState>> _cardKeys = [];
-  int _frontCardCount = 0;
-  final List<int> _frontCardIndexes = [];
 
   @override
   void initState() {
     super.initState();
 
+    print('initState');
+    _flipCardCore.toggleCardToFrontStream.stream.listen((_) {
+      _toggleCardToFront();
+    });
+
     reset();
   }
 
   void reset() {
-    // add 2 times
-    _randomImageNames.clear();
-    _randomImageNames.addAll(_imageNames);
-    _randomImageNames.addAll(_imageNames);
-
-    // shuffle
-    _randomImageNames.shuffle();
+    _flipCardCore.reset();
 
     // create global key
     _cardKeys.clear();
-    _cardKeys.addAll(_randomImageNames.map((_) => GlobalKey<FlipCardState>()));
+    _cardKeys.addAll(_flipCardCore
+        .getRandomCardImages()
+        .map((_) => GlobalKey<FlipCardState>()));
   }
 
   @override
@@ -70,66 +62,52 @@ class _MyHomePageState extends State<MyHomePage> {
       appBar: AppBar(
         title: Text(widget.title),
       ),
-      body: Center(
-        child: Wrap(
-          spacing: 4,
-          runSpacing: 4,
-          children: List.generate(
-            _randomImageNames.length,
-            (index) {
-              if (_randomImageNames[index].isEmpty) {
-                return Container(
-                  width: 100,
-                  height: 150,
-                  color: Colors.transparent,
-                );
-              }
-              return FlipCard(
-                key: _cardKeys[index],
-                onFlip: () {
-                  _frontCardCount++;
-                  _frontCardIndexes.add(index);
-                },
-                onFlipDone: (bool) {
-                  if (_frontCardCount == 2) {
-                    _toggleCardToFront();
-
-                    _checkCardIsEqual();
-
-                    _frontCardCount = 0;
-
-                    if (_frontCardIndexes.length >= 2) {
-                      String firstCardName = _randomImageNames[_frontCardIndexes[0]];
-                      String secondCardName = _randomImageNames[_frontCardIndexes[1]];
-                      if (firstCardName == secondCardName) {
-                        _randomImageNames[_frontCardIndexes[0]] = '';
-                        _randomImageNames[_frontCardIndexes[1]] = '';
-
-                        setState(() {});
-                      }
-                    }
-
-                    _frontCardIndexes.clear();
-                    _frontCardCount = 0;
+      body: StreamBuilder(
+        stream: _flipCardCore.cardsMatchedStream.stream,
+        builder: (context, snapshot) {
+          List<String> _randomImageNames = _flipCardCore.getRandomCardImages();
+
+          return Center(
+            child: Wrap(
+              spacing: 4,
+              runSpacing: 4,
+              children: List.generate(
+                _randomImageNames.length,
+                (index) {
+                  if (_randomImageNames[index].isEmpty) {
+                    return Container(
+                      width: 100,
+                      height: 150,
+                      color: Colors.transparent,
+                    );
                   }
+                  return FlipCard(
+                    key: _cardKeys[index],
+                    onFlip: () {
+                      _flipCardCore.flipCard(index);
+                    },
+                    onFlipDone: (_) {
+                      _flipCardCore.checkCards();
+                    },
+                    front: Container(
+                      width: 100,
+                      height: 150,
+                      color: Colors.orange,
+                    ),
+                    back: Container(
+                      width: 100,
+                      height: 150,
+                      child: Image.asset(
+                        _randomImageNames[index],
+                        fit: BoxFit.cover,
+                      ),
+                    ),
+                  );
                 },
-                front: Container(
-                  width: 100,
-                  height: 150,
-                  color: Colors.orange,
-                ),
-                back: Container(
-                  width: 100,
-                  height: 150,
-                  child: Image.asset(
-                    _randomImageNames[index],
-                    fit: BoxFit.cover,
-                  ),
-                ),
-              );
-            },
-          ),
-        ),
+              ),
+            ),
+          );
+        },
       ),
       floatingActionButton: FloatingActionButton(
         onPressed: () {
@@ -152,20 +130,9 @@ class _MyHomePageState extends State<MyHomePage> {
     }
   }
 
-  void _checkCardIsEqual() {
-    print('_checkCardIsEqual');
-    print(_frontCardIndexes);
-    if (_frontCardIndexes.length >= 2) {
-      String firstCardName = _randomImageNames[_frontCardIndexes[0]];
-      String secondCardName = _randomImageNames[_frontCardIndexes[1]];
-      if (firstCardName == secondCardName) {
-        _randomImageNames[_frontCardIndexes[0]] = '';
-        _randomImageNames[_frontCardIndexes[1]] = '';
-
-        setState(() {});
-      }
-    }
-
-    _frontCardIndexes.clear();
+  @override
+  void dispose() {
+    super.dispose();
+    _flipCardCore.dispose();
   }
 }
diff --git a/pubspec.lock b/pubspec.lock
index 4bbf272..f6fd949 100644
--- a/pubspec.lock
+++ b/pubspec.lock
@@ -7,7 +7,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.8.1"
+    version: "2.9.0"
   boolean_selector:
     dependency: transitive
     description:
@@ -21,28 +21,21 @@ packages:
       name: characters
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0"
-  charcode:
-    dependency: transitive
-    description:
-      name: charcode
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.3.1"
+    version: "1.2.1"
   clock:
     dependency: transitive
     description:
       name: clock
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0"
+    version: "1.1.1"
   collection:
     dependency: transitive
     description:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.15.0"
+    version: "1.16.0"
   cupertino_icons:
     dependency: "direct main"
     description:
@@ -56,7 +49,7 @@ packages:
       name: fake_async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0"
+    version: "1.3.1"
   flip_card:
     dependency: "direct main"
     description:
@@ -94,21 +87,28 @@ packages:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.10"
+    version: "0.12.12"
+  material_color_utilities:
+    dependency: transitive
+    description:
+      name: material_color_utilities
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "0.1.5"
   meta:
     dependency: transitive
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.7.0"
+    version: "1.8.0"
   path:
     dependency: transitive
     description:
       name: path
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.8.0"
+    version: "1.8.2"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -120,7 +120,7 @@ packages:
       name: source_span
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.8.1"
+    version: "1.9.0"
   stack_trace:
     dependency: transitive
     description:
@@ -141,34 +141,27 @@ packages:
       name: string_scanner
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0"
+    version: "1.1.1"
   term_glyph:
     dependency: transitive
     description:
       name: term_glyph
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0"
+    version: "1.2.1"
   test_api:
     dependency: transitive
     description:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.4.2"
-  typed_data:
-    dependency: transitive
-    description:
-      name: typed_data
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.3.0"
+    version: "0.4.12"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.0"
+    version: "2.1.2"
 sdks:
-  dart: ">=2.12.0 <3.0.0"
+  dart: ">=2.17.0-0 <3.0.0"