diff --git a/main.py b/main.py
index afb7f5c..bffd55e 100755
--- a/main.py
+++ b/main.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 from numba import jit
 
-from math import copysign, pi
+from math import copysign, pi, acos
 from time import time
 
 import pygame