diff --git a/program/Appconfig.cs b/program/Appconfig.cs
index e56a470..8eb2fec 100644
--- a/program/Appconfig.cs
+++ b/program/Appconfig.cs
@@ -3,7 +3,18 @@
 
 public static class AppConfig
 {
-    // Computed once, cached forever — reading it anywhere costs nothing.
-    public static readonly bool DebugMode =
-        Environment.GetCommandLineArgs().Contains("--debug");
+    // // Computed once, cached forever — reading it anywhere costs nothing.
+    // public static readonly bool DebugMode =
+    //     Environment.GetCommandLineArgs().Contains("--debug");
+
+    public static readonly bool DebugMode = Compute();
+
+    private static bool Compute()
+    {
+        var argv = Environment.GetCommandLineArgs();
+        Console.WriteLine("argv = [" + string.Join(" | ", argv) + "]");
+        return argv.Contains("--debug")
+            || Environment.GetEnvironmentVariable("EARS_DEBUG") == "1";
+    }
+    
 }
\ No newline at end of file
diff --git a/program/MainWindow.cs b/program/MainWindow.cs
index 57012d9..b7828c5 100644
--- a/program/MainWindow.cs
+++ b/program/MainWindow.cs
@@ -28,6 +28,12 @@
     [UI] private Button SettingButton = null;
     [UI] private Image  ConnectionIcon = null;   // was GtkIconView in the old glade
 
+    [UI] private Label ConnectionAlertLabel = null;
+
+    private uint _retryTimerId;
+    private bool _probing;
+    private const uint RetryMs = 1000;
+
     private CssProvider _scaleCssProvider;
     // private CssProvider _languageCssProvider;
     private int _lastAppliedWidth = -1;
@@ -122,6 +128,8 @@
         _Language.Register("LanguageLabel",  LanguageLabel);
         _Language.Register("LanguageToggle", LanguageToggle);
         _Language.RegisterDynamic("ConnectionIcon", ConnectionIcon);
+        ConnectionAlertLabel.Name = "ConnectionAlertLabel";
+        _Language.Register("ConnectionAlertLabel", ConnectionAlertLabel);
 
         _settingsWindow = new SettingsWindow(builder, _arduino, _Language);
         _settingsWindow.BackRequested += OnSettingsClosed;
@@ -204,7 +212,18 @@
         Option1Button.Sensitive = allowFullAccess;
         Option2Button.Sensitive = allowFullAccess;
         Option3Button.Sensitive = allowFullAccess;
-        SettingButton.Sensitive = true;   // always reachable, device or not
+        // SettingButton.Sensitive = true;   // always reachable, device or not
+
+        if (ConnectionAlertLabel != null)
+        {
+            ConnectionAlertLabel.Visible = !connected;
+            var ctx = ConnectionAlertLabel.StyleContext;
+            if (connected) ctx.RemoveClass("alert");
+            else           ctx.AddClass("alert");
+        }
+
+         if (connected || AppConfig.DebugMode) StopAutoRetry();
+        else StartAutoRetry();
 
         if (ConnectionIcon == null) return;
 
@@ -217,6 +236,41 @@
             : _Language["ConnectionIcon.Disconnected"];
     }
 
+    private void StartAutoRetry()
+    {
+        if (_retryTimerId != 0) return;
+        _retryTimerId = GLib.Timeout.Add(RetryMs, OnRetryTick);
+    }
+
+    private void StopAutoRetry()
+    {
+        if (_retryTimerId != 0)
+        {
+            GLib.Source.Remove(_retryTimerId);
+            _retryTimerId = 0;
+        }
+    }
+
+    private bool OnRetryTick()
+    {
+        if (_arduino.IsOpen) { _retryTimerId = 0; return false; }
+        if (_probing) return true;          // scan still running — don't stack them
+
+        _probing = true;
+        _arduino.DetectPortAsync().ContinueWith(t =>
+        {
+            string port = t.IsFaulted ? null : t.Result;
+            // DetectPortAsync runs off the UI thread; Connect() touches GLib.
+            Gtk.Application.Invoke((s, e) =>
+            {
+                _probing = false;
+                if (port != null && !_arduino.IsOpen)
+                    _arduino.Connect(port);   // fires ConnectionChanged(true)
+            });
+        });
+        return true;
+    }
+
     // ---------- localisation ----------
 
     // private Dictionary<string, string> LoadButtonText(string path)
diff --git a/program/homepageallv7.glade b/program/homepageallv7.glade
index 0b06dc9..0d81a6d 100644
--- a/program/homepageallv7.glade
+++ b/program/homepageallv7.glade
@@ -164,6 +164,21 @@
                 <property name="top-attach">3</property>
               </packing>
             </child>
+            <child>
+              <object class="GtkLabel" id="ConnectionAlertLabel">
+                <property name="visible">True</property>
+                <property name="can-focus">False</property>
+                <property name="halign">center</property>
+                <property name="valign">center</property>
+                <property name="hexpand">True</property>
+                <property name="label" translatable="yes">Problem connecting with device</property>
+              </object>
+              <packing>
+                <property name="left-attach">0</property>
+                <property name="top-attach">4</property>
+                <property name="width">2</property>
+              </packing>
+            </child>
           </object>
         </child>
         <child>
diff --git a/program/info_eng.csv b/program/info_eng.csv
index 04cbb7e..02440d3 100644
--- a/program/info_eng.csv
+++ b/program/info_eng.csv
@@ -25,4 +25,5 @@
 Log.EspNowConnected,[ESP-NOW] Peer connected
 Log.EspNowDisconnected,[ESP-NOW] Peer disconnected
 SoundBackButton,Back
-MapBackButton,Back
\ No newline at end of file
+MapBackButton,Back
+ConnectionAlertLabel,Problem connecting with device
\ No newline at end of file
diff --git a/program/info_jpn.csv b/program/info_jpn.csv
index a7ec241..23de4cb 100644
--- a/program/info_jpn.csv
+++ b/program/info_jpn.csv
@@ -25,4 +25,5 @@
 Log.EspNowConnected,[ESP-NOW] 相手が接続しました
 Log.EspNowDisconnected,[ESP-NOW] 相手が切断しました
 SoundBackButton,戻る
-MapBackButton,戻る
\ No newline at end of file
+MapBackButton,戻る
+ConnectionAlertLabel,デバイスに接続できません 
\ No newline at end of file
diff --git a/program/touch_friendly.css b/program/touch_friendly.css
index 3284f41..207a7d8 100644
--- a/program/touch_friendly.css
+++ b/program/touch_friendly.css
@@ -188,4 +188,24 @@
     background-color: #ffffff;
     font-size: 16px;
 }
-window.popup list row label { color: #111111; }
\ No newline at end of file
+window.popup list row label { color: #111111; }
+
+/* inactive buttons */
+/* splash: modes unavailable until the device connects */
+#Option1Button:disabled, #Option2Button:disabled, #Option3Button:disabled {
+    background-color: #A8AFA0;
+    border-color: rgba(0,0,0,0.25);
+}
+#Option1Button:disabled label,
+#Option2Button:disabled label,
+#Option3Button:disabled label { color: #EFEFEF; }
+
+#ConnectionAlertLabel {
+    font-family: 'Noto Sans JP', 'IPAPGothic', sans-serif;
+    font-size: 22px;
+    font-weight: 700;
+    color: #ffffff;
+    background-color: #C62828;
+    padding: 10px 24px;
+    margin: 8px 40px;
+}
\ No newline at end of file