diff --git a/Assets/Util.cs b/Assets/Util.cs
index 312a991..93d9a8e 100644
--- a/Assets/Util.cs
+++ b/Assets/Util.cs
@@ -1,4 +1,5 @@
-using UnityEngine;
+using UnityEditor;
+using UnityEngine;
 
 public class Util {
     public static Vector2 RotateBy(Vector2 v, float a) {
@@ -8,4 +9,23 @@ public class Util {
 
         return new Vector2((float) rx, (float) (v.x * sa + v.y * ca));
     }
+
+    public class ReadOnlyAttribute : PropertyAttribute {
+    }
+
+    [CustomPropertyDrawer(typeof(ReadOnlyAttribute))]
+    public class ReadOnlyDrawer : PropertyDrawer {
+        public override float GetPropertyHeight(SerializedProperty property,
+            GUIContent label) {
+            return EditorGUI.GetPropertyHeight(property, label, true);
+        }
+
+        public override void OnGUI(Rect position,
+            SerializedProperty property,
+            GUIContent label) {
+            GUI.enabled = false;
+            EditorGUI.PropertyField(position, property, label, true);
+            GUI.enabled = true;
+        }
+    }
 }
\ No newline at end of file