Elo system update

Assets/Scripts/UI/UIManager.cs

@@ -65,13 +65,30 @@ namespace Hallucinate.UI
 
         private void Awake()
         {
+            if (Instance != null && Instance != this)
+            {
+                Destroy(gameObject);
+                return;
+            }
             Instance = this;
+            DontDestroyOnLoad(gameObject);
+
             _uiDocument = GetComponent<UIDocument>();
             UnityEngine.Cursor.visible = false;
             
             ApplySavedUIScale();
         }
 
+        public void OnGameStarted()
+        {
+            _ = Push<HUDController>();
+        }
+
+        public void OnBackToMenu()
+        {
+            _ = Push<MainMenuController>();
+        }
+
         public void SetUIScale(float scale)
         {
             if (_uiDocument == null || _uiDocument.panelSettings == null) return;
@@ -187,7 +204,7 @@ namespace Hallucinate.UI
 
         private void Update()
         {
-            if (_mainMenuController != null) _mainMenuController.Update();
+            if (_history.Count > 0) _history.Peek().Update();
             UpdateCursorAndTrail();
         }