android/gradle.properties

 org.gradle.jvmargs=-Xmx1536M
 android.useAndroidX=true
 android.enableJetifier=true
-app.versionName=1.2.12
-app.versionCode=18
+app.versionName=1.2.13
+app.versionCode=19

lib/main.dart

 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
+import 'package:flutter/services.dart';
 
 import 'provider/data.dart';
 import 'screens/home.dart';
 
-void main() => runApp(MyApp());
+void main() {
+  WidgetsFlutterBinding.ensureInitialized();
+  SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp])
+      .then((value) => runApp(MyApp()));
+}
 
 class MyApp extends StatelessWidget {
   @override

lib/provider/data.dart

@@ -2,44 +2,61 @@ import 'package:flutter/foundation.dart';
 
 class Data extends ChangeNotifier {
 
-  // randomization
   bool _searchingCategory = false;
   bool _searchingLetter = false;
+
   String _category = '';
   String _letter = '';
+
   int _countdown = -1;
 
-  bool get searchingCategory => _searchingCategory;
+  final int _recentCategoriesCount = 15;
+  final int _recentLettersCount = 10;
+  List _recentCategories = [];
+  List _recentLetters = [];
+
 
-  set searchingCategory(bool value) {
+  bool get searchingCategory => _searchingCategory;
+  void setSearchingCategory(bool value) {
     _searchingCategory = value;
     notifyListeners();
   }
 
   bool get searchingLetter => _searchingLetter;
-
-  set searchingLetter(bool value) {
+  void setSearchingLetter(bool value) {
     _searchingLetter = value;
     notifyListeners();
   }
 
   String get category => _category;
-
-  set updateCategory(String value) {
+  void updateCategory(String value) {
     _category = value;
+    if (value != null && value != '') {
+      _recentCategories.insert(0, value);
+      _recentCategories = _recentCategories.take(_recentCategoriesCount).toList();
+    }
     notifyListeners();
   }
 
   String get letter => _letter;
-
-  set updateLetter(String value) {
+  void updateLetter(String value) {
     _letter = value;
+    if (value != null && value != '') {
+      _recentLetters.insert(0, value);
+      _recentLetters = _recentLetters.take(_recentLettersCount).toList();
+    }
     notifyListeners();
   }
 
-  int get countdown => _countdown;
+  String recentlyPickedLetter(int count) {
+    if (_recentLetters.length > count) {
+      return _recentLetters[count];
+    }
+    return '';
+  }
 
-  set updateCountdown(int value) {
+  int get countdown => _countdown;
+  void updateCountdown(int value) {
     _countdown = value;
     notifyListeners();
   }

lib/screens/home.dart

@@ -30,7 +30,7 @@ class Home extends StatelessWidget {
       dispose();
     }
     _countdownStart = 10;
-    myProvider.updateCountdown = _countdownStart;
+    myProvider.updateCountdown(_countdownStart);
     _timer = new Timer.periodic(
       oneSec,
       (Timer timer) {
@@ -38,7 +38,7 @@ class Home extends StatelessWidget {
           timer.cancel();
         } else {
           _countdownStart--;
-          myProvider.updateCountdown = _countdownStart;
+          myProvider.updateCountdown(_countdownStart);
         }
       },
     );
@@ -50,15 +50,15 @@ class Home extends StatelessWidget {
   }
 
   Future<void> pickCategory(Data myProvider) async {
-    myProvider.searchingCategory = true;
+    myProvider.setSearchingCategory(true);
     RandomPickCategory randomPickCategory;
     int attempts = 0;
     do {
       randomPickCategory = RandomPickCategory();
       await randomPickCategory.init();
       if (randomPickCategory.category != null) {
-        myProvider.updateCategory = randomPickCategory.category;
-        myProvider.searchingCategory = false;
+        myProvider.updateCategory(randomPickCategory.category);
+        myProvider.setSearchingCategory(false);
         break;
       }
       attempts++;
@@ -66,15 +66,15 @@ class Home extends StatelessWidget {
   }
 
   Future<void> pickLetter(Data myProvider) async {
-    myProvider.searchingLetter = true;
+    myProvider.setSearchingLetter(true);
     RandomPickLetter randomPickLetter;
     int attempts = 0;
     do {
       randomPickLetter = RandomPickLetter();
       await randomPickLetter.init();
       if (randomPickLetter.letter != null) {
-        myProvider.updateLetter = randomPickLetter.letter;
-        myProvider.searchingLetter = false;
+        myProvider.updateLetter(randomPickLetter.letter);
+        myProvider.setSearchingLetter(false);
         break;
       }
       attempts++;
@@ -87,15 +87,10 @@ class Home extends StatelessWidget {
     return hslDark.toColor();
   }
 
-  Container _buildPickedLetterContainer(Data myProvider, Color backgroundColor, double borderWidth) {
+  Container mainLetterButtonContainer(Data myProvider, Color backgroundColor, double borderWidth) {
     Color borderColor = darken(backgroundColor);
 
     return Container(
-      child: Column(
-        mainAxisSize: MainAxisSize.min,
-        mainAxisAlignment: MainAxisAlignment.center,
-        children: [
-          Container(
       margin: EdgeInsets.all(borderWidth),
       padding: EdgeInsets.all(borderWidth),
       decoration: BoxDecoration(
@@ -117,9 +112,85 @@ class Home extends StatelessWidget {
           ),
         ),
       ),
+    );
+  }
+
+  Container previousLetterBlockContainer(Data myProvider, int position, bool displayed) {
+    double spacingWidth = 2;
+    double borderWidth = 3;
+    Color backgroundColor = Colors.grey;
+    Color borderColor = darken(backgroundColor);
+    Color fontColor = Colors.black;
+
+    String letter = myProvider.recentlyPickedLetter(position);
+
+    if (letter == '' || displayed == false) {
+      backgroundColor = Colors.white;
+      borderColor = Colors.white;
+      fontColor = Colors.white;
+    }
+
+    return Container(
+      margin: EdgeInsets.all(spacingWidth),
+      padding: EdgeInsets.all(spacingWidth),
+      decoration: BoxDecoration(
+        color: backgroundColor,
+        borderRadius: BorderRadius.circular(borderWidth),
+        border: Border.all(
+          color: borderColor,
+          width: borderWidth,
+        ),
+      ),
+      child: Text(
+        ' ' + letter + ' ',
+        style: TextStyle(
+          fontSize: 35.0 - (7 * position),
+          fontWeight: FontWeight.w600,
+          color: fontColor,
+        ),
       ),
-        ],
+    );
+  }
+
+  Container _buildPickedLetterContainer(Data myProvider, Color backgroundColor, double borderWidth) {
+    int previousLettersCountToShow = 3;
+
+    List <Widget> cells = [];
+
+    // Add previous letters blocks
+    for (var i = 0; i < previousLettersCountToShow; i++) {
+      cells.add(TableCell(
+        verticalAlignment: TableCellVerticalAlignment.middle,
+        child: previousLetterBlockContainer(myProvider, previousLettersCountToShow - i, true)
+      ));
+    }
+
+    // Add current letter block
+    cells.add(TableCell(
+      verticalAlignment: TableCellVerticalAlignment.middle,
+      child: mainLetterButtonContainer(myProvider, backgroundColor, borderWidth)
+    ));
+
+    // Pad with empty blocks to keep symetrical layout
+    for (var i = 0; i < previousLettersCountToShow; i++) {
+      cells.add(TableCell(
+        verticalAlignment: TableCellVerticalAlignment.middle,
+        child: previousLetterBlockContainer(myProvider, i + 1, false)
+      ));
+    }
+
+    return Container(
+      margin: EdgeInsets.all(2),
+      padding: EdgeInsets.all(2),
+
+      child: Table(
+        defaultColumnWidth: IntrinsicColumnWidth(),
+        children: [
+          TableRow(
+            children: cells
           ),
+        ]
+      )
     );
   }
 

pubspec.lock

@@ -7,7 +7,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.6.1"
+    version: "2.7.0"
   boolean_selector:
     dependency: transitive
     description:
@@ -28,7 +28,7 @@ packages:
       name: charcode
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0"
+    version: "1.3.1"
   clock:
     dependency: transitive
     description:
@@ -73,7 +73,7 @@ packages:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.3.0"
+    version: "1.7.0"
   nested:
     dependency: transitive
     description:
@@ -141,7 +141,7 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.3.0"
+    version: "0.4.1"
   typed_data:
     dependency: transitive
     description: