diff --git a/src/Mono.cs b/src/Mono.cs
index 968971c..ddf72ca 100644
--- a/src/Mono.cs
+++ b/src/Mono.cs
@@ -248,6 +248,23 @@ static class Mono
         }
     }
 
+    static int[] GetShuffledIndices<T>(T[] array)
+    {
+        int[] indices = new int[array.Length];
+        for (int i = 0; i < array.Length; i++)
+        {
+            indices[i] = i;
+        }
+        for (int i = indices.Length - 1; i > 0; i--)
+        {
+            int j = System.Random.Shared.Next(i + 1);
+            int temp = indices[i];
+            indices[i] = indices[j];
+            indices[j] = temp;
+        }
+        return indices;
+    }
+
     // directions for moving in the grid
     static readonly XYZi[] directions = new XYZi[]
     {