diff --git a/example/lib/data.dart b/example/lib/data.dart
index 58d3681..17666c6 100644
--- a/example/lib/data.dart
+++ b/example/lib/data.dart
@@ -1,6 +1,6 @@
 class Place {
-  final String name;
-  final String url;
+  final String? name;
+  final String? url;
 
   const Place({this.name, this.url});
 }
diff --git a/example/lib/sample2.dart b/example/lib/sample2.dart
index ed99c14..7ae1ad2 100644
--- a/example/lib/sample2.dart
+++ b/example/lib/sample2.dart
@@ -19,7 +19,7 @@ class Sample2 extends StatelessWidget {
                   (item) => Stack(
                     children: [
                       Image.network(
-                        item.url,
+                        item.url!,
                         height: height,
                         fit: BoxFit.cover,
                       ),
@@ -37,7 +37,7 @@ class Sample2 extends StatelessWidget {
                               ),
                             ]),
                             child: Text(
-                              item.name,
+                              item.name!,
                               style: Theme.of(context).textTheme.title,
                             ),
                           ),
diff --git a/example/lib/sample3.dart b/example/lib/sample3.dart
index 5b8f46a..05e2f7e 100644
--- a/example/lib/sample3.dart
+++ b/example/lib/sample3.dart
@@ -20,7 +20,7 @@ class Sample3 extends StatelessWidget {
             itemBuilder: (context, index, notifier) {
               final item = places[index];
               final transform = Matrix4.identity();
-              final t = (index - notifier).abs();
+              final t = (index - notifier!).abs();
               final scale = lerpDouble(1.5, 0, t);
               transform.scale(scale, scale);
               return CubeWidget(
@@ -29,7 +29,7 @@ class Sample3 extends StatelessWidget {
                 child: Stack(
                   children: [
                     Image.network(
-                      item.url,
+                      item.url!,
                       height: height,
                       fit: BoxFit.cover,
                     ),
@@ -48,7 +48,7 @@ class Sample3 extends StatelessWidget {
                               ),
                             ]),
                             child: Text(
-                              item.name.split('-').join('\n'),
+                              item.name!.split('-').join('\n'),
                               textAlign: TextAlign.center,
                               style: Theme.of(context).textTheme.title,
                             ),
diff --git a/example/pubspec.lock b/example/pubspec.lock
index 67304a9..2aa68fb 100644
--- a/example/pubspec.lock
+++ b/example/pubspec.lock
@@ -1,62 +1,48 @@
 # Generated by pub
 # See https://dart.dev/tools/pub/glossary#lockfile
 packages:
-  archive:
-    dependency: transitive
-    description:
-      name: archive
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.11"
-  args:
-    dependency: transitive
-    description:
-      name: args
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.5.2"
   async:
     dependency: transitive
     description:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.4.0"
+    version: "2.6.1"
   boolean_selector:
     dependency: transitive
     description:
       name: boolean_selector
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.5"
-  charcode:
+    version: "2.1.0"
+  characters:
     dependency: transitive
     description:
-      name: charcode
+      name: characters
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.2"
-  collection:
+    version: "1.1.0"
+  charcode:
     dependency: transitive
     description:
-      name: collection
+      name: charcode
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.14.11"
-  convert:
+    version: "1.2.0"
+  clock:
     dependency: transitive
     description:
-      name: convert
+      name: clock
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.1"
-  crypto:
+    version: "1.1.0"
+  collection:
     dependency: transitive
     description:
-      name: crypto
+      name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.3"
+    version: "1.15.0"
   cube_transition:
     dependency: "direct main"
     description:
@@ -64,6 +50,13 @@ packages:
       relative: true
     source: path
     version: "1.0.2"
+  fake_async:
+    dependency: transitive
+    description:
+      name: fake_async
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.2.0"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -74,55 +67,27 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
-  image:
-    dependency: transitive
-    description:
-      name: image
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.1.4"
   matcher:
     dependency: transitive
     description:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.6"
+    version: "0.12.10"
   meta:
     dependency: transitive
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.8"
+    version: "1.3.0"
   path:
     dependency: transitive
     description:
       name: path
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.6.4"
-  pedantic:
-    dependency: transitive
-    description:
-      name: pedantic
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.8.0+1"
-  petitparser:
-    dependency: transitive
-    description:
-      name: petitparser
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.4.0"
-  quiver:
-    dependency: transitive
-    description:
-      name: quiver
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.5"
+    version: "1.8.0"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -134,62 +99,55 @@ packages:
       name: source_span
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.5.5"
+    version: "1.8.1"
   stack_trace:
     dependency: transitive
     description:
       name: stack_trace
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.3"
+    version: "1.10.0"
   stream_channel:
     dependency: transitive
     description:
       name: stream_channel
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.0"
+    version: "2.1.0"
   string_scanner:
     dependency: transitive
     description:
       name: string_scanner
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.5"
+    version: "1.1.0"
   term_glyph:
     dependency: transitive
     description:
       name: term_glyph
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0"
+    version: "1.2.0"
   test_api:
     dependency: transitive
     description:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.11"
+    version: "0.3.0"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.6"
+    version: "1.3.0"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.8"
-  xml:
-    dependency: transitive
-    description:
-      name: xml
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "3.5.0"
+    version: "2.1.0"
 sdks:
-  dart: ">=2.4.0 <3.0.0"
+  dart: ">=2.12.0 <3.0.0"
diff --git a/example/pubspec.yaml b/example/pubspec.yaml
index d022690..d371a2e 100644
--- a/example/pubspec.yaml
+++ b/example/pubspec.yaml
@@ -14,7 +14,7 @@ description: A new Flutter project.
 version: 1.0.0+1
 
 environment:
-  sdk: ">=2.3.0 <3.0.0"
+  sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
   flutter:
diff --git a/example/test/widget_test.dart b/example/test/widget_test.dart
new file mode 100644
index 0000000..747db1d
--- /dev/null
+++ b/example/test/widget_test.dart
@@ -0,0 +1,30 @@
+// This is a basic Flutter widget test.
+//
+// To perform an interaction with a widget in your test, use the WidgetTester
+// utility that Flutter provides. For example, you can send tap and scroll
+// gestures. You can also use WidgetTester to find child widgets in the widget
+// tree, read text, and verify that the values of widget properties are correct.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:example/main.dart';
+
+void main() {
+  testWidgets('Counter increments smoke test', (WidgetTester tester) async {
+    // Build our app and trigger a frame.
+    await tester.pumpWidget(MyApp());
+
+    // Verify that our counter starts at 0.
+    expect(find.text('0'), findsOneWidget);
+    expect(find.text('1'), findsNothing);
+
+    // Tap the '+' icon and trigger a frame.
+    await tester.tap(find.byIcon(Icons.add));
+    await tester.pump();
+
+    // Verify that our counter has incremented.
+    expect(find.text('0'), findsNothing);
+    expect(find.text('1'), findsOneWidget);
+  });
+}
diff --git a/example/web/favicon.png b/example/web/favicon.png
new file mode 100644
index 0000000..8aaa46a
Binary files /dev/null and b/example/web/favicon.png differ
diff --git a/example/web/icons/Icon-192.png b/example/web/icons/Icon-192.png
new file mode 100644
index 0000000..b749bfe
Binary files /dev/null and b/example/web/icons/Icon-192.png differ
diff --git a/example/web/icons/Icon-512.png b/example/web/icons/Icon-512.png
new file mode 100644
index 0000000..88cfd48
Binary files /dev/null and b/example/web/icons/Icon-512.png differ
diff --git a/example/web/index.html b/example/web/index.html
new file mode 100644
index 0000000..0081e18
--- /dev/null
+++ b/example/web/index.html
@@ -0,0 +1,98 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <!--
+    If you are serving your web app in a path other than the root, change the
+    href value below to reflect the base path you are serving from.
+
+    The path provided below has to start and end with a slash "/" in order for
+    it to work correctly.
+
+    For more details:
+    * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/base
+  -->
+  <base href="/">
+
+  <meta charset="UTF-8">
+  <meta content="IE=Edge" http-equiv="X-UA-Compatible">
+  <meta name="description" content="A new Flutter project.">
+
+  <!-- iOS meta tags & icons -->
+  <meta name="apple-mobile-web-app-capable" content="yes">
+  <meta name="apple-mobile-web-app-status-bar-style" content="black">
+  <meta name="apple-mobile-web-app-title" content="example">
+  <link rel="apple-touch-icon" href="icons/Icon-192.png">
+
+  <title>example</title>
+  <link rel="manifest" href="manifest.json">
+</head>
+<body>
+  <!-- This script installs service_worker.js to provide PWA functionality to
+       application. For more information, see:
+       https://developers.google.com/web/fundamentals/primers/service-workers -->
+  <script>
+    var serviceWorkerVersion = null;
+    var scriptLoaded = false;
+    function loadMainDartJs() {
+      if (scriptLoaded) {
+        return;
+      }
+      scriptLoaded = true;
+      var scriptTag = document.createElement('script');
+      scriptTag.src = 'main.dart.js';
+      scriptTag.type = 'application/javascript';
+      document.body.append(scriptTag);
+    }
+
+    if ('serviceWorker' in navigator) {
+      // Service workers are supported. Use them.
+      window.addEventListener('load', function () {
+        // Wait for registration to finish before dropping the <script> tag.
+        // Otherwise, the browser will load the script multiple times,
+        // potentially different versions.
+        var serviceWorkerUrl = 'flutter_service_worker.js?v=' + serviceWorkerVersion;
+        navigator.serviceWorker.register(serviceWorkerUrl)
+          .then((reg) => {
+            function waitForActivation(serviceWorker) {
+              serviceWorker.addEventListener('statechange', () => {
+                if (serviceWorker.state == 'activated') {
+                  console.log('Installed new service worker.');
+                  loadMainDartJs();
+                }
+              });
+            }
+            if (!reg.active && (reg.installing || reg.waiting)) {
+              // No active web worker and we have installed or are installing
+              // one for the first time. Simply wait for it to activate.
+              waitForActivation(reg.installing ?? reg.waiting);
+            } else if (!reg.active.scriptURL.endsWith(serviceWorkerVersion)) {
+              // When the app updates the serviceWorkerVersion changes, so we
+              // need to ask the service worker to update.
+              console.log('New service worker available.');
+              reg.update();
+              waitForActivation(reg.installing);
+            } else {
+              // Existing service worker is still good.
+              console.log('Loading app from service worker.');
+              loadMainDartJs();
+            }
+          });
+
+        // If service worker doesn't succeed in a reasonable amount of time,
+        // fallback to plaint <script> tag.
+        setTimeout(() => {
+          if (!scriptLoaded) {
+            console.warn(
+              'Failed to load app from service worker. Falling back to plain <script> tag.',
+            );
+            loadMainDartJs();
+          }
+        }, 4000);
+      });
+    } else {
+      // Service workers not supported. Just drop the <script> tag.
+      loadMainDartJs();
+    }
+  </script>
+</body>
+</html>
diff --git a/example/web/manifest.json b/example/web/manifest.json
new file mode 100644
index 0000000..8c01291
--- /dev/null
+++ b/example/web/manifest.json
@@ -0,0 +1,23 @@
+{
+    "name": "example",
+    "short_name": "example",
+    "start_url": ".",
+    "display": "standalone",
+    "background_color": "#0175C2",
+    "theme_color": "#0175C2",
+    "description": "A new Flutter project.",
+    "orientation": "portrait-primary",
+    "prefer_related_applications": false,
+    "icons": [
+        {
+            "src": "icons/Icon-192.png",
+            "sizes": "192x192",
+            "type": "image/png"
+        },
+        {
+            "src": "icons/Icon-512.png",
+            "sizes": "512x512",
+            "type": "image/png"
+        }
+    ]
+}
diff --git a/lib/src/cube_page_route.dart b/lib/src/cube_page_route.dart
index 319eba5..27bdfe4 100644
--- a/lib/src/cube_page_route.dart
+++ b/lib/src/cube_page_route.dart
@@ -11,10 +11,10 @@ class CubePageRoute extends PageRouteBuilder {
   final Duration duration;
 
   /// The next page we will show
-  final Widget enterPage;
+  final Widget? enterPage;
 
   /// The current page we will dismiss
-  final Widget exitPage;
+  final Widget? exitPage;
 
   /// Background color used when the transition is running , it's [Colors.black] as default
   final Color backgroundColor;
@@ -28,7 +28,7 @@ class CubePageRoute extends PageRouteBuilder {
     ),
   }) : super(
           transitionDuration: duration,
-          pageBuilder: (context, animation, secondaryAnimation) => enterPage,
+          pageBuilder: (context, animation, secondaryAnimation) => enterPage!,
           transitionsBuilder: (context, animation, secondaryAnimation, child) {
             return Container(
               color: backgroundColor,
diff --git a/lib/src/cube_page_view.dart b/lib/src/cube_page_view.dart
index fa31ecc..48df8e8 100644
--- a/lib/src/cube_page_view.dart
+++ b/lib/src/cube_page_view.dart
@@ -7,7 +7,7 @@ import 'package:flutter/material.dart';
 /// Used by [CubePageView.builder] and other APIs that use lazily-generated widgets.
 ///
 typedef CubeWidgetBuilder = CubeWidget Function(
-    BuildContext context, int index, double pageNotifier);
+    BuildContext context, int index, double? pageNotifier);
 
 /// This Widget has the [PageView] widget inside.
 /// It works in two modes :
@@ -16,28 +16,28 @@ typedef CubeWidgetBuilder = CubeWidget Function(
 
 class CubePageView extends StatefulWidget {
   /// Called whenever the page in the center of the viewport changes.
-  final ValueChanged<int> onPageChanged;
+  final ValueChanged<int>? onPageChanged;
 
   /// An object that can be used to control the position to which this page
   /// view is scrolled.
-  final PageController controller;
+  final PageController? controller;
 
   /// Builder to customize your items
-  final CubeWidgetBuilder itemBuilder;
+  final CubeWidgetBuilder? itemBuilder;
 
   /// The number of items you have, this is only required if you use [CubePageView.builder]
-  final int itemCount;
+  final int? itemCount;
 
   /// Widgets you want to use inside the [CubePageView], this is only required if you use [CubePageView] constructor
-  final List<Widget> children;
+  final List<Widget>? children;
 
   /// Creates a scrollable list that works page by page from an explicit [List]
   /// of widgets.
   const CubePageView({
-    Key key,
+    Key? key,
     this.onPageChanged,
     this.controller,
-    @required this.children,
+    required List<Widget> this.children,
   })  : itemBuilder = null,
         itemCount = null,
         assert(children != null),
@@ -55,9 +55,9 @@ class CubePageView extends StatefulWidget {
   /// zero and less than [itemCount].
 
   CubePageView.builder({
-    Key key,
-    @required this.itemCount,
-    @required this.itemBuilder,
+    Key? key,
+    required int this.itemCount,
+    required this.itemBuilder,
     this.onPageChanged,
     this.controller,
   })  : this.children = null,
@@ -71,25 +71,25 @@ class CubePageView extends StatefulWidget {
 
 class _CubePageViewState extends State<CubePageView> {
   final _pageNotifier = ValueNotifier(0.0);
-  PageController _pageController;
+  PageController? _pageController;
 
   void _listener() {
-    _pageNotifier.value = _pageController.page;
+    _pageNotifier.value = _pageController!.page ?? 0;
   }
 
   @override
   void initState() {
     _pageController = widget.controller ?? PageController();
-    WidgetsBinding.instance.addPostFrameCallback((_) {
-      _pageController.addListener(_listener);
+    WidgetsBinding.instance!.addPostFrameCallback((_) {
+      _pageController!.addListener(_listener);
     });
     super.initState();
   }
 
   @override
   void dispose() {
-    _pageController.removeListener(_listener);
-    _pageController.dispose();
+    _pageController!.removeListener(_listener);
+    _pageController!.dispose();
     _pageNotifier.dispose();
     super.dispose();
   }
@@ -99,18 +99,18 @@ class _CubePageViewState extends State<CubePageView> {
     return Material(
       color: Colors.transparent,
       child: Center(
-        child: ValueListenableBuilder<double>(
+        child: ValueListenableBuilder<double?>(
           valueListenable: _pageNotifier,
           builder: (_, value, child) => PageView.builder(
             controller: _pageController,
             onPageChanged: widget.onPageChanged,
             physics: const ClampingScrollPhysics(),
-            itemCount: widget.itemCount ?? widget.children.length,
+            itemCount: widget.itemCount ?? widget.children!.length,
             itemBuilder: (_, index) {
               if (widget.itemBuilder != null)
-                return widget.itemBuilder(context, index, value);
+                return widget.itemBuilder!(context, index, value);
               return CubeWidget(
-                child: widget.children[index],
+                child: widget.children![index],
                 index: index,
                 pageNotifier: value,
               );
@@ -130,27 +130,27 @@ class CubeWidget extends StatelessWidget {
   final int index;
 
   /// Page Notifier value, it comes from the [CubeWidgetBuilder]
-  final double pageNotifier;
+  final double? pageNotifier;
 
   /// Child you want to use inside the Cube
   final Widget child;
 
   const CubeWidget({
-    Key key,
-    @required this.index,
-    @required this.pageNotifier,
-    @required this.child,
+    Key? key,
+    required this.index,
+    required this.pageNotifier,
+    required this.child,
   }) : super(key: key);
 
   @override
   Widget build(BuildContext context) {
-    final isLeaving = (index - pageNotifier) <= 0;
-    final t = (index - pageNotifier);
-    final rotationY = lerpDouble(0, 90, t);
-    final opacity = lerpDouble(0, 1, t.abs()).clamp(0.0, 1.0);
+    final isLeaving = (index - pageNotifier!) <= 0;
+    final t = (index - pageNotifier!);
+    final rotationY = lerpDouble(0, 90, t)!;
+    final num opacity = lerpDouble(0, 1, t.abs())!.clamp(0.0, 1.0);
     final transform = Matrix4.identity();
     transform.setEntry(3, 2, 0.003);
-    transform.rotateY(-degToRad(rotationY));
+    transform.rotateY(-degToRad(rotationY) as double);
     return Transform(
       alignment: isLeaving ? Alignment.centerRight : Alignment.centerLeft,
       transform: transform,
@@ -159,7 +159,7 @@ class CubeWidget extends StatelessWidget {
           child,
           Positioned.fill(
             child: Opacity(
-              opacity: opacity,
+              opacity: opacity as double,
               child: Container(
                 child: Container(
                   color: Colors.black87,
diff --git a/pubspec.lock b/pubspec.lock
index f85e4f2..a22483c 100644
--- a/pubspec.lock
+++ b/pubspec.lock
@@ -1,13 +1,20 @@
 # Generated by pub
 # See https://dart.dev/tools/pub/glossary#lockfile
 packages:
+  characters:
+    dependency: transitive
+    description:
+      name: characters
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.1.0"
   collection:
     dependency: transitive
     description:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.14.11"
+    version: "1.15.0"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -19,7 +26,7 @@ packages:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.8"
+    version: "1.3.0"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -31,13 +38,13 @@ packages:
       name: typed_data
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.6"
+    version: "1.3.0"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.8"
+    version: "2.1.0"
 sdks:
-  dart: ">=2.3.0 <3.0.0"
+  dart: ">=2.12.0 <3.0.0"
diff --git a/pubspec.yaml b/pubspec.yaml
index a74616a..72dd311 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -6,7 +6,7 @@ homepage: https://aeyrium.com/products/mxtracker/
 repository: https://github.com/aeyrium/cube_transition
 
 environment:
-  sdk: ">=2.3.0 <3.0.0"
+  sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
   flutter: