Code cleanup.

Assets/Cryville/Crtr/UI/Master.cs

@@ -1,12 +1,24 @@
+using System;
 using UnityEngine;
 
 namespace Cryville.Crtr.UI {
 	internal class Master : MonoBehaviour {
+		static Master s_instance;
+		public static Master Instance { get { return s_instance; } }
+
 #pragma warning disable IDE0044
 		[SerializeField]
 		private GameObject m_menu;
 #pragma warning restore IDE0044
 
+		void Awake() {
+			if (s_instance != null) {
+				Destroy(gameObject);
+				throw new InvalidOperationException("Attempted to initialize a singleton twice.");
+			}
+			s_instance = this;
+		}
+
 		internal void ShowMenu() { m_menu.SetActive(true); }
 		internal void HideMenu() { m_menu.SetActive(false); }