diff --git a/src/Mono.cs b/src/Mono.cs
index 118b300..a195efb 100644
--- a/src/Mono.cs
+++ b/src/Mono.cs
@@ -22,6 +22,15 @@ static class Mono
         s_array = new(SD_X, SD_Y, SD_Z, -1),
         tail_fill = new(SD_X, SD_Y, SD_Z, -1);
 
+    static void update_s_array()
+    {
+        s_array.Clear(-1);
+        for (int i = 0; i < snake_len; i++)
+        {
+            s_array[snake[i]] = i;
+        }
+    }
+
     public static XYZi[] snake = new XYZi[
         Maths.u_length(SD_X) * Maths.u_length(SD_Y) * Maths.u_length(SD_Z)
     ];
@@ -52,6 +61,7 @@ static class Mono
         {
             snake[i] = new XYZi(0, 0, 0);
         }
+        update_s_array();
     }
 
     public static void Frame()
@@ -185,11 +195,7 @@ static class Mono
             holes.Remove(snake[snake_len - 1]);
         }
 
-        s_array.Clear(-1);
-        for (int i = 0; i < snake_len; i++)
-        {
-            s_array[snake[i]] = i;
-        }
+        update_s_array();
 
         // eat
         if (!eaten_latch.state)