diff --git a/app/src/main/java/com/example/notesai/MainActivity.kt b/app/src/main/java/com/example/notesai/MainActivity.kt
index a920e2f..2db6961 100644
--- a/app/src/main/java/com/example/notesai/MainActivity.kt
+++ b/app/src/main/java/com/example/notesai/MainActivity.kt
@@ -40,52 +40,95 @@ class MainActivity : ComponentActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContent {
-            MaterialTheme(
-                colorScheme = darkColorScheme(
-                    primary = AppColors.Primary,
-                    onPrimary = Color.White,
-                    primaryContainer = AppColors.Primary.copy(alpha = 0.3f),
-                    onPrimaryContainer = Color.White,
-                    secondary = AppColors.Secondary,
-                    onSecondary = Color.White,
-                    secondaryContainer = AppColors.Secondary.copy(alpha = 0.3f),
-                    onSecondaryContainer = Color.White,
-                    background = AppColors.Background,
-                    onBackground = AppColors.OnBackground,
-                    surface = AppColors.Surface,
-                    onSurface = AppColors.OnSurface,
-                    surfaceVariant = AppColors.SurfaceVariant,
-                    onSurfaceVariant = AppColors.OnSurfaceVariant,
-                    error = AppColors.Error,
-                    onError = Color.White,
-                    outline = AppColors.Border,
-                    outlineVariant = AppColors.Divider
-                ),
-                typography = Typography(
-                    displayLarge = MaterialTheme.typography.displayLarge.copy(
-                        fontWeight = FontWeight.Bold
-                    ),
-                    headlineLarge = MaterialTheme.typography.headlineLarge.copy(
-                        fontWeight = FontWeight.Bold
-                    ),
-                    titleLarge = MaterialTheme.typography.titleLarge.copy(
-                        fontWeight = FontWeight.SemiBold
-                    ),
-                    bodyLarge = MaterialTheme.typography.bodyLarge.copy(
-                        lineHeight = 24.sp
-                    ),
-                    bodyMedium = MaterialTheme.typography.bodyMedium.copy(
-                        lineHeight = 20.sp
-                    )
-                )
-            ) {
-                Surface(
-                    modifier = Modifier.fillMaxSize(),
-                    color = MaterialTheme.colorScheme.background
-                ) {
-                    NotesApp()
-                }
-            }
+            NotesAppTheme()
+        }
+    }
+}
+
+@Composable
+fun NotesAppTheme(content: @Composable () -> Unit = { NotesApp() }) {
+    val context = LocalContext.current
+    val dataStoreManager = remember { DataStoreManager(context) }
+    var isDarkTheme by remember { mutableStateOf(true) }
+
+    // Load theme preference
+    LaunchedEffect(Unit) {
+        dataStoreManager.themeFlow.collect { theme ->
+            isDarkTheme = theme == "dark"
+            AppColors.setTheme(isDarkTheme)
+        }
+    }
+
+    // Create dynamic color scheme based on theme
+    val colorScheme = if (isDarkTheme) {
+        darkColorScheme(
+            primary = AppColors.Primary,
+            onPrimary = Color.White,
+            primaryContainer = AppColors.Primary.copy(alpha = 0.3f),
+            onPrimaryContainer = Color.White,
+            secondary = AppColors.Secondary,
+            onSecondary = Color.White,
+            secondaryContainer = AppColors.Secondary.copy(alpha = 0.3f),
+            onSecondaryContainer = Color.White,
+            background = AppColors.Background,
+            onBackground = AppColors.OnBackground,
+            surface = AppColors.Surface,
+            onSurface = AppColors.OnSurface,
+            surfaceVariant = AppColors.SurfaceVariant,
+            onSurfaceVariant = AppColors.OnSurfaceVariant,
+            error = AppColors.Error,
+            onError = Color.White,
+            outline = AppColors.Border,
+            outlineVariant = AppColors.Divider
+        )
+    } else {
+        lightColorScheme(
+            primary = AppColors.Primary,
+            onPrimary = Color.White,
+            primaryContainer = AppColors.Primary.copy(alpha = 0.1f),
+            onPrimaryContainer = AppColors.Primary,
+            secondary = AppColors.Secondary,
+            onSecondary = Color.White,
+            secondaryContainer = AppColors.Secondary.copy(alpha = 0.1f),
+            onSecondaryContainer = AppColors.Secondary,
+            background = AppColors.Background,
+            onBackground = AppColors.OnBackground,
+            surface = AppColors.Surface,
+            onSurface = AppColors.OnSurface,
+            surfaceVariant = AppColors.SurfaceVariant,
+            onSurfaceVariant = AppColors.OnSurfaceVariant,
+            error = AppColors.Error,
+            onError = Color.White,
+            outline = AppColors.Border,
+            outlineVariant = AppColors.Divider
+        )
+    }
+
+    MaterialTheme(
+        colorScheme = colorScheme,
+        typography = Typography(
+            displayLarge = MaterialTheme.typography.displayLarge.copy(
+                fontWeight = FontWeight.Bold
+            ),
+            headlineLarge = MaterialTheme.typography.headlineLarge.copy(
+                fontWeight = FontWeight.Bold
+            ),
+            titleLarge = MaterialTheme.typography.titleLarge.copy(
+                fontWeight = FontWeight.SemiBold
+            ),
+            bodyLarge = MaterialTheme.typography.bodyLarge.copy(
+                lineHeight = 24.sp
+            ),
+            bodyMedium = MaterialTheme.typography.bodyMedium.copy(
+                lineHeight = 20.sp
+            )
+        )
+    ) {
+        Surface(
+            modifier = Modifier.fillMaxSize(),
+            color = MaterialTheme.colorScheme.background
+        ) {
+            content()
         }
     }
 }
@@ -529,6 +572,4 @@ fun NotesApp() {
             )
         }
     }
-}
-
-private fun AppColors.setTheme(darkTheme: Boolean) {}
\ No newline at end of file
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/example/notesai/util/Constants.kt b/app/src/main/java/com/example/notesai/util/Constants.kt
index 26f630d..8a4991f 100644
--- a/app/src/main/java/com/example/notesai/util/Constants.kt
+++ b/app/src/main/java/com/example/notesai/util/Constants.kt
@@ -1,34 +1,77 @@
 package com.example.notesai.util
 
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.graphics.Color
 
 object AppColors {
+    // Theme state
+    private var isDarkTheme by mutableStateOf(true)
+
     // Primary Colors
-    val Primary = Color(0xFF6C63FF)
-    val Secondary = Color(0xFF03DAC6)
-    val Accent = Color(0xFFFF6B9D)
+    val Primary: Color
+        get() = if (isDarkTheme) Color(0xFF6C63FF) else Color(0xFF5A52D5)
+
+    val Secondary: Color
+        get() = if (isDarkTheme) Color(0xFF03DAC6) else Color(0xFF018786)
+
+    val Accent: Color
+        get() = if (isDarkTheme) Color(0xFFFF6B9D) else Color(0xFFE91E63)
 
     // Background Colors
-    val Background = Color(0xFF121212)
-    val Surface = Color(0xFF1E1E1E)
-    val SurfaceVariant = Color(0xFF2A2A2A)
-    val SurfaceElevated = Color(0xFF252525)
+    val Background: Color
+        get() = if (isDarkTheme) Color(0xFF121212) else Color(0xFFFAFAFA)
+
+    val Surface: Color
+        get() = if (isDarkTheme) Color(0xFF1E1E1E) else Color(0xFFFFFFFF)
+
+    val SurfaceVariant: Color
+        get() = if (isDarkTheme) Color(0xFF2A2A2A) else Color(0xFFF5F5F5)
+
+    val SurfaceElevated: Color
+        get() = if (isDarkTheme) Color(0xFF252525) else Color(0xFFFFFFFF)
 
     // Text Colors
-    val OnBackground = Color(0xFFE1E1E1)
-    val OnSurface = Color(0xFFCCCCCC)
-    val OnSurfaceVariant = Color(0xFF9E9E9E)
-    val OnSurfaceTertiary = Color(0xFF757575)
+    val OnBackground: Color
+        get() = if (isDarkTheme) Color(0xFFE1E1E1) else Color(0xFF1C1B1F)
+
+    val OnSurface: Color
+        get() = if (isDarkTheme) Color(0xFFCCCCCC) else Color(0xFF1C1B1F)
+
+    val OnSurfaceVariant: Color
+        get() = if (isDarkTheme) Color(0xFF9E9E9E) else Color(0xFF49454F)
+
+    val OnSurfaceTertiary: Color
+        get() = if (isDarkTheme) Color(0xFF757575) else Color(0xFF79747E)
 
     // Utility Colors
-    val Error = Color(0xFFCF6679)
-    val Warning = Color(0xFFFFB74D)
-    val Success = Color(0xFF81C784)
-    val Info = Color(0xFF64B5F6)
+    val Error: Color
+        get() = if (isDarkTheme) Color(0xFFCF6679) else Color(0xFFB3261E)
+
+    val Warning: Color
+        get() = if (isDarkTheme) Color(0xFFFFB74D) else Color(0xFFF57C00)
+
+    val Success: Color
+        get() = if (isDarkTheme) Color(0xFF81C784) else Color(0xFF388E3C)
+
+    val Info: Color
+        get() = if (isDarkTheme) Color(0xFF64B5F6) else Color(0xFF1976D2)
 
     // Border & Divider
-    val Border = Color(0xFF3A3A3A)
-    val Divider = Color(0xFF2E2E2E)
+    val Border: Color
+        get() = if (isDarkTheme) Color(0xFF3A3A3A) else Color(0xFFE0E0E0)
+
+    val Divider: Color
+        get() = if (isDarkTheme) Color(0xFF2E2E2E) else Color(0xFFE0E0E0)
+
+    // Function to update theme
+    fun setTheme(darkTheme: Boolean) {
+        isDarkTheme = darkTheme
+    }
+
+    // Get current theme state
+    fun isDark(): Boolean = isDarkTheme
 }
 
 object Constants {