diff --git a/field.py b/field.py
index 3f1242e..f17813f 100644
--- a/field.py
+++ b/field.py
@@ -53,8 +53,8 @@ class Field():
                       for rows in range(Field.HEIGHT)]
 
     def reset_half_field(self):
-        self.state = [[' ' for cols in range(Field.WIDTH)]
-                      for rows in range(int(Field.HEIGHT/2))]
+        for row in range(int(self.HEIGHT/2)):
+            self.state[row] = [' ' for cols in range(Field.WIDTH)]
 
     def rotate_state(self):
         self.state = self.rotate_90_degree_anticlckwise(self.state)