diff --git a/app/build.gradle.kts b/app/build.gradle.kts
index 086f40d..e99e79f 100644
--- a/app/build.gradle.kts
+++ b/app/build.gradle.kts
@@ -40,6 +40,8 @@ android {
 }
 
 dependencies {
+
+    //Android Studio Auto-Gen
     implementation(libs.androidx.core.ktx)
     implementation(libs.androidx.lifecycle.runtime.ktx)
     implementation(libs.androidx.activity.compose)
@@ -55,4 +57,7 @@ dependencies {
     androidTestImplementation(libs.androidx.compose.ui.test.junit4)
     debugImplementation(libs.androidx.compose.ui.tooling)
     debugImplementation(libs.androidx.compose.ui.test.manifest)
+
+    //Manually added
+    implementation("androidx.datastore:datastore-preferences:1.2.0")
 }
\ No newline at end of file
diff --git a/app/src/main/java/de/miaurizius/shap_planner/UserPreferences.kt b/app/src/main/java/de/miaurizius/shap_planner/UserPreferences.kt
new file mode 100644
index 0000000..852816d
--- /dev/null
+++ b/app/src/main/java/de/miaurizius/shap_planner/UserPreferences.kt
@@ -0,0 +1,39 @@
+package de.miaurizius.shap_planner
+
+import android.content.Context
+import androidx.datastore.preferences.core.booleanPreferencesKey
+import androidx.datastore.preferences.core.edit
+import androidx.datastore.preferences.core.stringPreferencesKey
+import androidx.datastore.preferences.preferencesDataStore
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.map
+
+val Context.dataStore by preferencesDataStore(name = "user_prefs")
+
+object UserPreferencesKeys {
+    val IS_LOGGED_IN = booleanPreferencesKey("is_logged_in")
+    val LAST_USER_ID = stringPreferencesKey("last_user_id")
+}
+
+class UserPreferences(private val context: Context) {
+
+    //Stave status
+    suspend fun saveLogin(userId: String) {
+        context.dataStore.edit { prefs ->
+            prefs[UserPreferencesKeys.IS_LOGGED_IN] = true
+            prefs[UserPreferencesKeys.LAST_USER_ID] = userId;
+        }
+    }
+
+    //Logout
+    suspend fun clearLogin() {
+        context.dataStore.edit { prefs ->
+            prefs[UserPreferencesKeys.IS_LOGGED_IN] = false
+            prefs[UserPreferencesKeys.LAST_USER_ID] = ""
+        }
+    }
+
+    //Get state
+    val isLoggedInFlow: Flow<Boolean> = context.dataStore.data.map { prefs -> prefs[UserPreferencesKeys.IS_LOGGED_IN] ?: false }
+    val lastUserLoginFlow: Flow<String?> = context.dataStore.data.map { prefs -> prefs[UserPreferencesKeys.LAST_USER_ID] }
+}
\ No newline at end of file
diff --git a/app/src/main/java/de/miaurizius/shap_planner/activities/MainActivity.kt b/app/src/main/java/de/miaurizius/shap_planner/activities/MainActivity.kt
index c288778..d2c1e4e 100644
--- a/app/src/main/java/de/miaurizius/shap_planner/activities/MainActivity.kt
+++ b/app/src/main/java/de/miaurizius/shap_planner/activities/MainActivity.kt
@@ -4,44 +4,68 @@ import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
-import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
-import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Button
 import androidx.compose.material3.Text
+import androidx.compose.material3.TextField
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.tooling.preview.Preview
+import androidx.compose.ui.unit.dp
+import de.miaurizius.shap_planner.UserPreferences
 import de.miaurizius.shap_planner.ui.theme.ShapPlannerTheme
+import de.miaurizius.shap_planner.viewmodels.LoginViewModel
 
 class MainActivity : ComponentActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
-        enableEdgeToEdge()
+//        enableEdgeToEdge()
+
+        val prefs = UserPreferences(this)
+        val viewModel = LoginViewModel(prefs)
+
         setContent {
             ShapPlannerTheme {
-                Scaffold(modifier = Modifier.fillMaxSize()) { innerPadding ->
-                    Greeting(
-                        name = "Android",
-                        modifier = Modifier.padding(innerPadding)
-                    )
-                }
+                val isLoggedIn by viewModel.isLoggedIn.collectAsState()
+                if(isLoggedIn) MainScreen()
+                else LoginScreen { userId -> viewModel.login(userId) }
             }
         }
     }
 }
 
 @Composable
-fun Greeting(name: String, modifier: Modifier = Modifier) {
-    Text(
-        text = "Hello $name!",
-        modifier = modifier
-    )
+fun MainScreen() {
+    Column(modifier = Modifier.padding(16.dp)) {
+        Text("Willkommen zurück!")
+        Button(onClick = { /* TODO: Logout */ }) {
+            Text("Logout")
+        }
+    }
 }
 
-@Preview(showBackground = true)
 @Composable
-fun GreetingPreview() {
-    ShapPlannerTheme {
-        Greeting("Android")
+fun LoginScreen(onLogin: (String) -> Unit) {
+    var userId by remember { mutableStateOf("") }
+
+    Column(modifier = Modifier.padding(16.dp)) {
+        Text("Bitte anmelden")
+        Spacer(modifier = Modifier.height(8.dp))
+        TextField(
+            value = userId,
+            onValueChange = { userId = it },
+            label = { Text("User ID") }
+        )
+        Spacer(modifier = Modifier.height(8.dp))
+        Button(onClick = { if(userId.isNotEmpty()) onLogin(userId) }) {
+            Text("Login")
+        }
     }
 }
\ No newline at end of file
diff --git a/app/src/main/java/de/miaurizius/shap_planner/viewmodels/LoginViewModel.kt b/app/src/main/java/de/miaurizius/shap_planner/viewmodels/LoginViewModel.kt
new file mode 100644
index 0000000..e1ed193
--- /dev/null
+++ b/app/src/main/java/de/miaurizius/shap_planner/viewmodels/LoginViewModel.kt
@@ -0,0 +1,23 @@
+package de.miaurizius.shap_planner.viewmodels
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import de.miaurizius.shap_planner.UserPreferences
+import kotlinx.coroutines.flow.SharingStarted
+import kotlinx.coroutines.flow.stateIn
+import kotlinx.coroutines.launch
+
+class LoginViewModel(private val prefs: UserPreferences) : ViewModel() {
+
+    val isLoggedIn = prefs.isLoggedInFlow.stateIn(viewModelScope, SharingStarted.Lazily, false)
+    val lastUserId = prefs.lastUserLoginFlow.stateIn(viewModelScope, SharingStarted.Lazily, null)
+
+    fun login(userId: String) {
+        viewModelScope.launch { prefs.saveLogin(userId) }
+    }
+
+    fun logout() {
+        viewModelScope.launch { prefs.clearLogin() }
+    }
+
+}
\ No newline at end of file