lib/main.dart

@@ -33,7 +33,25 @@ class WkApp extends StatelessWidget {
     return MaterialApp(
       title: 'Hirameki SRS',
       debugShowCheckedModeBanner: false,
-      theme: ThemeData.dark(useMaterial3: true),
+      theme: ThemeData(
+        colorScheme: const ColorScheme(
+          brightness: Brightness.dark,
+          primary: Color(0xFF90CAF9), // Light blue for primary elements
+          onPrimary: Colors.black,
+          secondary: Color(0xFFBBDEFB), // Slightly lighter blue for secondary elements
+          onSecondary: Colors.black,
+          tertiary: Color(0xFFA5D6A7), // Light green for success/correct states
+          onTertiary: Colors.black,
+          error: Color(0xFFEF9A9A), // Light red for error states
+          onError: Colors.black,
+          surface: Color(0xFF121212), // Very dark gray
+          onSurface: Colors.white,
+          surfaceContainer: Color(0xFF1E1E1E), // Slightly lighter dark gray
+          surfaceContainerHighest: Color(0xFF424242), // A distinct dark gray for surface variants
+          onSurfaceVariant: Colors.white70,
+        ),
+        useMaterial3: true,
+      ),
       home: const StartScreen(),
     );
   }

lib/src/screens/home_screen.dart

@@ -326,11 +326,11 @@ class _HomeScreenState extends State<HomeScreen> with SingleTickerProviderStateM
       content: Text(
         isCorrect ? 'Correct!' : 'Wrong — correct: $correctDisplay',
         style: TextStyle(
-          color: isCorrect ? Colors.greenAccent : Colors.redAccent,
+          color: isCorrect ? Theme.of(context).colorScheme.primary : Theme.of(context).colorScheme.error,
           fontWeight: FontWeight.bold,
         ),
       ),
-      backgroundColor: const Color(0xFF222222),
+      backgroundColor: Theme.of(context).colorScheme.surfaceContainerHighest,
       duration: const Duration(milliseconds: 900),
     );
     if (mounted) {
@@ -341,7 +341,11 @@ class _HomeScreenState extends State<HomeScreen> with SingleTickerProviderStateM
       _isAnswering = true; // Disable input after showing result
     });
 
-    Future.delayed(const Duration(milliseconds: 900), () => _nextQuestion());
+    Future.delayed(const Duration(milliseconds: 900), () {
+      if (mounted) {
+        _nextQuestion();
+      }
+    });
   }
 
   @override
@@ -353,7 +357,7 @@ class _HomeScreenState extends State<HomeScreen> with SingleTickerProviderStateM
           child: Column(
             mainAxisAlignment: MainAxisAlignment.center,
             children: [
-              const Text('WaniKani API key is not set.', style: TextStyle(color: Colors.white)),
+              Text('WaniKani API key is not set.', style: TextStyle(color: Theme.of(context).colorScheme.onSurface)),
               const SizedBox(height: 16),
               ElevatedButton(
                 onPressed: () async {
@@ -382,7 +386,7 @@ class _HomeScreenState extends State<HomeScreen> with SingleTickerProviderStateM
           ],
         ),
       ),
-      backgroundColor: const Color(0xFF121212),
+      backgroundColor: Theme.of(context).colorScheme.surface,
       body: TabBarView(
         controller: _tabController,
         children: [
@@ -426,11 +430,11 @@ class _HomeScreenState extends State<HomeScreen> with SingleTickerProviderStateM
               Expanded(
                 child: Text(
                   _status,
-                  style: const TextStyle(color: Colors.white),
+                  style: TextStyle(color: Theme.of(context).colorScheme.onSurface),
                 ),
               ),
               if (_loading)
-                const CircularProgressIndicator(color: Colors.blueAccent),
+                CircularProgressIndicator(color: Theme.of(context).colorScheme.primary),
             ],
           ),
           const SizedBox(height: 18),
@@ -446,8 +450,8 @@ class _HomeScreenState extends State<HomeScreen> with SingleTickerProviderStateM
                 child: KanjiCard(
                   characters: prompt,
                   subtitle: subtitle,
-                  backgroundColor: const Color(0xFF1E1E1E),
-                  textColor: Colors.white,
+                  backgroundColor: Theme.of(context).colorScheme.surface,
+                  textColor: Theme.of(context).colorScheme.onSurface,
                 ),
               ),
             ),
@@ -468,7 +472,7 @@ class _HomeScreenState extends State<HomeScreen> with SingleTickerProviderStateM
                 const SizedBox(height: 8),
                 Text(
                   'Score: ${quizState.score} / ${quizState.asked}',
-                  style: const TextStyle(color: Colors.white),
+                  style: TextStyle(color: Theme.of(context).colorScheme.onSurface),
                 ),
               ],
             ),

lib/src/screens/start_screen.dart

@@ -28,8 +28,8 @@ class StartScreen extends StatelessWidget {
         decoration: BoxDecoration(
           gradient: LinearGradient(
             colors: [
-              const Color(0xFF121212),
-              Colors.grey[900]!,
+              Theme.of(context).colorScheme.surface,
+              Theme.of(context).colorScheme.surface,
             ],
             begin: Alignment.topLeft,
             end: Alignment.bottomRight,
@@ -113,14 +113,18 @@ class StartScreen extends StatelessWidget {
               const SizedBox(height: 16),
               Text(
                 title,
-                style: const TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
+                style: Theme.of(context).textTheme.titleMedium?.copyWith(
+                  fontWeight: FontWeight.bold,
+                ),
                 textAlign: TextAlign.center,
               ),
               const SizedBox(height: 8),
               Expanded(
                 child: Text(
                   description,
-                  style: const TextStyle(fontSize: 12, color: Colors.grey),
+                  style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                    color: Theme.of(context).colorScheme.onSurfaceVariant,
+                  ),
                   textAlign: TextAlign.center,
                   softWrap: true,
                 ),

lib/src/widgets/options_grid.dart

@@ -40,9 +40,9 @@ class OptionsGrid extends StatelessWidget {
 
         if (showResult) {
           if (correctAnswers != null && correctAnswers!.contains(o)) {
-            currentButtonColor = Colors.green;
+            currentButtonColor = theme.colorScheme.tertiary;
           } else if (o == selectedOption) {
-            currentButtonColor = Colors.red;
+            currentButtonColor = theme.colorScheme.error;
           }
         }
 
@@ -60,7 +60,7 @@ class OptionsGrid extends StatelessWidget {
             ),
             child: Text(
               o,
-              style: TextStyle(fontSize: 20, color: currentTextColor),
+              style: theme.textTheme.titleMedium?.copyWith(color: currentTextColor),
               textAlign: TextAlign.center,
             ),
           ),