program terminates when window closes now.

drawing.py

@@ -4,7 +4,8 @@ from turtle import (
     goto,
     pensize,
     begin_fill,
-    end_fill
+    end_fill, 
+    mainloop
 )
 from math import sin, cos, tau, pi
 
@@ -29,4 +30,4 @@ for i in range(segments + 1):
     goto(coords[i])
 right(90)
 end_fill()
-input()
+mainloop()