Update

Assets/Scripts/UI/UIManager.cs

@@ -63,6 +63,9 @@ namespace Hallucinate.UI
 
         private const string UI_SCALE_KEY = "UIScale";
 
+        [Header("Development Settings")]
+        [SerializeField] private bool allowMultipleInstances = true;
+
         private void Awake()
         {
             if (Instance != null && Instance != this)
@@ -73,6 +76,19 @@ namespace Hallucinate.UI
             Instance = this;
             DontDestroyOnLoad(gameObject);
 
+            // Single instance guard
+            if (!Application.isEditor && !allowMultipleInstances)
+            {
+                var currentProcess = System.Diagnostics.Process.GetCurrentProcess();
+                var processes = System.Diagnostics.Process.GetProcessesByName(currentProcess.ProcessName);
+                if (processes.Length > 1)
+                {
+                    Debug.LogError("[UIManager] Another instance is already running. Quitting to prevent save conflict.");
+                    Application.Quit();
+                    return;
+                }
+            }
+
             _uiDocument = GetComponent<UIDocument>();
             UnityEngine.Cursor.visible = false;
             
@@ -92,10 +108,10 @@ namespace Hallucinate.UI
         public void SetUIScale(float scale)
         {
             if (_uiDocument == null || _uiDocument.panelSettings == null) return;
-            
+
             // Unity UI Toolkit dùng panelSettings để điều khiển tỉ lệ
-            // Chúng ta thay đổi scale multiplier
-            _uiDocument.panelSettings.scale = scale;
+            // Chúng ta thay đổi scale multiplier. Mặc định 1.0 sẽ tương ứng với visual scale là 1.3
+            _uiDocument.panelSettings.scale = scale * 1.3f;
             PlayerPrefs.SetFloat(UI_SCALE_KEY, scale);
             PlayerPrefs.Save();
         }
@@ -105,7 +121,6 @@ namespace Hallucinate.UI
             float savedScale = PlayerPrefs.GetFloat(UI_SCALE_KEY, 1.0f);
             SetUIScale(savedScale);
         }
-
         private void Start()
         {
             if (_uiDocument == null) _uiDocument = GetComponent<UIDocument>();