diff --git a/example/pubspec.lock b/example/pubspec.lock
index 1e55e0d..c35d60f 100644
--- a/example/pubspec.lock
+++ b/example/pubspec.lock
@@ -21,28 +21,42 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.4.0"
+    version: "2.8.1"
   boolean_selector:
     dependency: transitive
     description:
       name: boolean_selector
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.5"
+    version: "2.1.0"
+  characters:
+    dependency: transitive
+    description:
+      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: "1.1.2"
+    version: "1.3.1"
+  clock:
+    dependency: transitive
+    description:
+      name: clock
+      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"
   convert:
     dependency: transitive
     description:
@@ -64,6 +78,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "0.1.2"
+  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
@@ -101,28 +122,21 @@ packages:
       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: "1.7.0"
   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"
+    version: "1.8.0"
   petitparser:
     dependency: transitive
     description:
@@ -130,13 +144,6 @@ packages:
       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"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -148,56 +155,56 @@ 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: "0.4.2"
   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"
+    version: "2.1.0"
   xml:
     dependency: transitive
     description:
@@ -213,4 +220,4 @@ packages:
     source: hosted
     version: "2.2.0"
 sdks:
-  dart: ">=2.4.0 <3.0.0"
+  dart: ">=2.12.0 <3.0.0"
diff --git a/lib/src/calculator.dart b/lib/src/calculator.dart
index 489d095..9fec945 100644
--- a/lib/src/calculator.dart
+++ b/lib/src/calculator.dart
@@ -95,7 +95,7 @@ class _CalculatorState extends State<Calculator> {
                 minFontSize: 14.0,
                 style: TextStyle(
                   fontSize: 14.0 * 3.0,
-                  color: theme.primaryTextTheme.title.color,
+                  color: theme.primaryTextTheme.headline1.color,
                 ),
                 textAlign: TextAlign.right,
                 cursorColor: Colors.grey,
diff --git a/lib/src/keypad.dart b/lib/src/keypad.dart
index 1d1ccdf..3f7b224 100644
--- a/lib/src/keypad.dart
+++ b/lib/src/keypad.dart
@@ -129,7 +129,7 @@ class _KeyPadState extends State<KeyPad> {
         child: Text(
           symbol.text,
           style: TextStyle(
-            color: isClear ? theme.primaryTextTheme.title.color : Colors.grey,
+            color: isClear ? theme.primaryTextTheme.headline1.color : Colors.grey,
             fontSize: 14.0 * 3.0,
           ),
         ),
@@ -194,7 +194,7 @@ class _KeyPadState extends State<KeyPad> {
         opPadColor = theme.primaryColor;
         opPad = Text(
           symbol.text,
-          style: TextStyle(color: theme.primaryTextTheme.title.color, fontSize: fontSize),
+          style: TextStyle(color: theme.primaryTextTheme.headline1.color, fontSize: fontSize),
         );
         break;
       default:
diff --git a/lib/src/math_formula_view.dart b/lib/src/math_formula_view.dart
index 90ccd6c..046c4d7 100644
--- a/lib/src/math_formula_view.dart
+++ b/lib/src/math_formula_view.dart
@@ -84,7 +84,7 @@ class _MathFormulaViewState extends State<MathFormulaView> {
       minFontSize: 12.0,
       style: TextStyle(
         fontSize: 14.0 * 2.0,
-        color: theme.primaryTextTheme.title.color,
+        color: theme.primaryTextTheme.headline1.color,
       ),
       textAlign: TextAlign.right,
       cursorColor: Colors.grey,
diff --git a/pubspec.lock b/pubspec.lock
index a1c2b1d..3bf2ec7 100644
--- a/pubspec.lock
+++ b/pubspec.lock
@@ -1,83 +1,111 @@
 # Generated by pub
 # See https://dart.dev/tools/pub/glossary#lockfile
 packages:
-  analyzer:
+  _fe_analyzer_shared:
     dependency: transitive
     description:
-      name: analyzer
+      name: _fe_analyzer_shared
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.36.4"
-  archive:
+    version: "28.0.0"
+  analyzer:
     dependency: transitive
     description:
-      name: archive
+      name: analyzer
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.11"
+    version: "2.5.0"
   args:
     dependency: transitive
     description:
       name: args
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.5.2"
+    version: "2.3.0"
   async:
     dependency: transitive
     description:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.4.0"
+    version: "2.8.1"
   boolean_selector:
     dependency: transitive
     description:
       name: boolean_selector
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.5"
+    version: "2.1.0"
+  characters:
+    dependency: transitive
+    description:
+      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: "1.1.2"
+    version: "1.3.1"
+  cli_util:
+    dependency: transitive
+    description:
+      name: cli_util
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "0.3.4"
+  clock:
+    dependency: transitive
+    description:
+      name: clock
+      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"
   convert:
     dependency: transitive
     description:
       name: convert
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.1"
+    version: "3.0.1"
   coverage:
     dependency: transitive
     description:
       name: coverage
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.13.3+3"
+    version: "1.0.3"
   crypto:
     dependency: transitive
     description:
       name: crypto
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.3"
-  csslib:
+    version: "3.0.1"
+  fake_async:
+    dependency: transitive
+    description:
+      name: fake_async
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.2.0"
+  file:
     dependency: transitive
     description:
-      name: csslib
+      name: file
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.16.1"
+    version: "6.1.2"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -88,216 +116,146 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
-  front_end:
+  frontend_server_client:
     dependency: transitive
     description:
-      name: front_end
+      name: frontend_server_client
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.1.19"
+    version: "2.1.2"
   glob:
     dependency: transitive
     description:
       name: glob
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0"
-  html:
-    dependency: transitive
-    description:
-      name: html
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "0.14.0+3"
-  http:
-    dependency: transitive
-    description:
-      name: http
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "0.12.0+2"
+    version: "2.0.2"
   http_multi_server:
     dependency: transitive
     description:
       name: http_multi_server
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.0"
+    version: "3.0.1"
   http_parser:
     dependency: transitive
     description:
       name: http_parser
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "3.1.3"
-  image:
-    dependency: transitive
-    description:
-      name: image
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.1.4"
+    version: "4.0.0"
   io:
     dependency: transitive
     description:
       name: io
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.3.3"
+    version: "1.0.3"
   js:
     dependency: transitive
     description:
       name: js
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.6.1+1"
-  kernel:
-    dependency: transitive
-    description:
-      name: kernel
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "0.3.19"
+    version: "0.6.3"
   logging:
     dependency: transitive
     description:
       name: logging
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.11.3+2"
+    version: "1.0.2"
   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: "1.7.0"
   mime:
     dependency: transitive
     description:
       name: mime
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.9.6+3"
-  multi_server_socket:
-    dependency: transitive
-    description:
-      name: multi_server_socket
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.0.2"
-  node_interop:
-    dependency: transitive
-    description:
-      name: node_interop
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.0.3"
-  node_io:
-    dependency: transitive
-    description:
-      name: node_io
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.0.1+2"
+    version: "1.0.0"
   node_preamble:
     dependency: transitive
     description:
       name: node_preamble
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.4.8"
+    version: "2.0.1"
   package_config:
     dependency: transitive
     description:
       name: package_config
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0"
-  package_resolver:
-    dependency: transitive
-    description:
-      name: package_resolver
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.0.10"
+    version: "2.0.2"
   path:
     dependency: transitive
     description:
       name: path
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.6.4"
+    version: "1.8.0"
   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"
+    version: "1.11.1"
   pool:
     dependency: transitive
     description:
       name: pool
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.4.0"
+    version: "1.5.0"
   pub_semver:
     dependency: transitive
     description:
       name: pub_semver
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.4.2"
-  quiver:
-    dependency: transitive
-    description:
-      name: quiver
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.5"
+    version: "2.1.0"
   shelf:
     dependency: transitive
     description:
       name: shelf
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.7.5"
+    version: "1.2.0"
   shelf_packages_handler:
     dependency: transitive
     description:
       name: shelf_packages_handler
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.4"
+    version: "3.0.0"
   shelf_static:
     dependency: transitive
     description:
       name: shelf_static
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.8"
+    version: "1.1.0"
   shelf_web_socket:
     dependency: transitive
     description:
       name: shelf_web_socket
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.3"
+    version: "1.0.1"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -309,118 +267,118 @@ packages:
       name: source_map_stack_trace
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.5"
+    version: "2.1.0"
   source_maps:
     dependency: transitive
     description:
       name: source_maps
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.10.8"
+    version: "0.10.10"
   source_span:
     dependency: transitive
     description:
       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:
     dependency: "direct dev"
     description:
       name: test
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.4"
+    version: "1.17.10"
   test_api:
     dependency: transitive
     description:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.11"
+    version: "0.4.2"
   test_core:
     dependency: transitive
     description:
       name: test_core
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.15"
+    version: "0.4.0"
   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"
+    version: "2.1.0"
   vm_service:
     dependency: transitive
     description:
       name: vm_service
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.3.1"
+    version: "7.3.0"
   watcher:
     dependency: transitive
     description:
       name: watcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.9.7+12"
+    version: "1.0.1"
   web_socket_channel:
     dependency: transitive
     description:
       name: web_socket_channel
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0"
-  xml:
+    version: "2.1.0"
+  webkit_inspection_protocol:
     dependency: transitive
     description:
-      name: xml
+      name: webkit_inspection_protocol
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "3.5.0"
+    version: "1.0.0"
   yaml:
     dependency: transitive
     description:
       name: yaml
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.2.0"
+    version: "3.1.0"
 sdks:
-  dart: ">=2.6.0 <3.0.0"
+  dart: ">=2.14.0 <3.0.0"
diff --git a/pubspec.yaml b/pubspec.yaml
index 4a38e19..536d5c2 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,11 +1,11 @@
 name: flutter_calculator
 description: A simple, smart and powerful flutter calculator widget.
-version: 0.2.0
+version: 0.3.0
 author: flytreeleft <flytreeleft@crazydan.org>
 homepage: https://github.com/flytreeleft/flutter_calculator
 
 environment:
-  sdk: ">=2.2.2 <3.0.0"
+  sdk: ">=2.7.0 <3.0.0"
 
 dependencies:
   flutter: