user can set url

.env

@@ -2,5 +2,5 @@
 # - Android emulator: use http://10.0.2.2:3001 (emulator's alias for host)
 # - iOS simulator: use http://localhost:3001
 # - Physical device: use your computer's IP, e.g. http://192.168.1.5:3001 (find IP in system settings)
-#API_BASE_URL=http://localhost:3001
+#API_BASE_URL=http://10.0.2.2:3001
-API_BASE_URL=http://10.0.2.2:3001
+API_BASE_URL=https://omotomo.satoshinakamoto.win

lib/env.dart

@@ -1,10 +1,48 @@
 import 'package:flutter_dotenv/flutter_dotenv.dart';
+import 'package:shared_preferences/shared_preferences.dart';
 
-/// API base URL (no trailing slash). Loaded from .env as API_BASE_URL.
+const String _overrideKey = 'api_base_url_override';
+
+String? _override;
+
+String _fromEnv() {
+  final raw = dotenv.env['API_BASE_URL']?.trim() ?? '';
+  final url = raw.replaceAll(' ', '');
+  if (url.isEmpty) return 'http://localhost:3001';
+  return url.endsWith('/') ? url.substring(0, url.length - 1) : url;
+}
+
+/// API base URL (no trailing slash). Uses in-app override if set, else .env.
+/// Strips spaces so accidental spaces don't break DNS.
 String get apiBaseUrl {
-  final url = dotenv.env['API_BASE_URL']?.trim();
+  if (_override != null && _override!.trim().isNotEmpty) {
-  if (url == null || url.isEmpty) {
+    final u = _override!.trim().replaceAll(' ', '');
-    return 'http://localhost:3001';
+    if (u.isNotEmpty) {
+      return u.endsWith('/') ? u.substring(0, u.length - 1) : u;
     }
-  return url.endsWith('/') ? url.substring(0, url.length - 1) : url;
+  }
+  return _fromEnv();
 }
+
+/// Load saved override from disk. Call once at startup.
+Future<void> loadApiBaseUrlOverride() async {
+  final prefs = await SharedPreferences.getInstance();
+  _override = prefs.getString(_overrideKey);
+}
+
+/// Save or clear the in-app base URL override. Pass null or empty to use .env again.
+Future<void> setApiBaseUrlOverride(String? value) async {
+  final prefs = await SharedPreferences.getInstance();
+  if (value == null || value.trim().isEmpty) {
+    await prefs.remove(_overrideKey);
+    _override = null;
+    return;
+  }
+  final u = value.trim().replaceAll(' ', '');
+  final withoutSlash = u.endsWith('/') ? u.substring(0, u.length - 1) : u;
+  await prefs.setString(_overrideKey, withoutSlash);
+  _override = withoutSlash;
+}
+
+/// Current default from .env (ignoring override). For display only.
+String get apiBaseUrlDefault => _fromEnv();

lib/main.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_dotenv/flutter_dotenv.dart';
 import 'routes.dart';
 import 'theme.dart';
+import 'env.dart';
 import 'services/api_auth_service.dart';
 import 'services/deck_storage.dart';
 
@@ -11,6 +12,7 @@ void main() async {
   await dotenv.load(fileName: '.env').catchError(
         (_) => dotenv.load(fileName: '.env.example'),
       );
+  await loadApiBaseUrlOverride();
 
   await DeckStorage().initialize();
   await ApiAuthService.instance.init();

lib/screens/login_screen.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 
+import '../env.dart';
 import '../services/api_auth_service.dart';
 
 class LoginScreen extends StatefulWidget {
@@ -13,19 +14,75 @@ class _LoginScreenState extends State<LoginScreen> {
   final _formKey = GlobalKey<FormState>();
   final _emailController = TextEditingController();
   final _passwordController = TextEditingController();
+  final _serverUrlController = TextEditingController();
   bool _loading = false;
   String? _errorMessage;
   bool _isRegister = false;
   final _displayNameController = TextEditingController();
 
+  @override
+  void initState() {
+    super.initState();
+    _serverUrlController.text = apiBaseUrl;
+  }
+
   @override
   void dispose() {
     _emailController.dispose();
     _passwordController.dispose();
+    _serverUrlController.dispose();
     _displayNameController.dispose();
     super.dispose();
   }
 
+  Future<void> _saveServerUrl() async {
+    final raw = _serverUrlController.text.trim().replaceAll(' ', '');
+    if (raw.isEmpty) {
+      await setApiBaseUrlOverride(null);
+      if (mounted) {
+        setState(() {
+          _serverUrlController.text = apiBaseUrlDefault;
+          _errorMessage = null;
+        });
+        ScaffoldMessenger.of(context).showSnackBar(
+          const SnackBar(content: Text('Using default server URL')),
+        );
+      }
+      return;
+    }
+    final withoutSlash = raw.endsWith('/') ? raw.substring(0, raw.length - 1) : raw;
+    final uri = Uri.tryParse(withoutSlash);
+    if (uri == null ||
+        (!uri.scheme.startsWith('http') || uri.host.isEmpty)) {
+      if (mounted) {
+        setState(() {
+          _errorMessage = 'Enter a valid URL (e.g. https://example.com)';
+        });
+      }
+      return;
+    }
+    await setApiBaseUrlOverride(withoutSlash);
+    if (mounted) {
+      setState(() => _errorMessage = null);
+      ScaffoldMessenger.of(context).showSnackBar(
+        const SnackBar(content: Text('Server URL saved')),
+      );
+    }
+  }
+
+  Future<void> _useDefaultServerUrl() async {
+    await setApiBaseUrlOverride(null);
+    if (mounted) {
+      setState(() {
+        _serverUrlController.text = apiBaseUrlDefault;
+        _errorMessage = null;
+      });
+      ScaffoldMessenger.of(context).showSnackBar(
+        const SnackBar(content: Text('Using default server URL')),
+      );
+    }
+  }
+
   Future<void> _submit() async {
     setState(() {
       _errorMessage = null;
@@ -113,6 +170,36 @@ class _LoginScreenState extends State<LoginScreen> {
                     return null;
                   },
                 ),
+                const SizedBox(height: 20),
+                Text(
+                  'Server URL',
+                  style: Theme.of(context).textTheme.titleSmall,
+                ),
+                const SizedBox(height: 8),
+                TextFormField(
+                  controller: _serverUrlController,
+                  decoration: const InputDecoration(
+                    hintText: 'Leave empty for app default',
+                    border: OutlineInputBorder(),
+                  ),
+                  keyboardType: TextInputType.url,
+                  autocorrect: false,
+                  textInputAction: TextInputAction.done,
+                ),
+                const SizedBox(height: 8),
+                Row(
+                  children: [
+                    FilledButton.tonal(
+                      onPressed: _loading ? null : _saveServerUrl,
+                      child: const Text('Save server URL'),
+                    ),
+                    const SizedBox(width: 12),
+                    TextButton(
+                      onPressed: _loading ? null : _useDefaultServerUrl,
+                      child: const Text('Use default'),
+                    ),
+                  ],
+                ),
                 if (_errorMessage != null) ...[
                   const SizedBox(height: 16),
                   Text(

lib/utils/connection_error.dart

@@ -10,6 +10,11 @@ String connectionErrorMessage(Object error) {
       error is http.ClientException ||
       error is HandshakeException ||
       error is TlsException) {
+    final msg = error.toString().toLowerCase();
+    if (msg.contains('host lookup') ||
+        msg.contains('no address associated with hostname')) {
+      return "This device can't resolve the server hostname. On an emulator, try setting DNS to 8.8.8.8 or use a real device.";
+    }
     return 'Connection to server has broken. Check API URL and network.';
   }
   return 'Network error. Please check the API URL and try again.';