diff --git a/labygui.py b/labygui.py
index d557d9b..78cce98 100644
--- a/labygui.py
+++ b/labygui.py
@@ -1,4 +1,4 @@
-from math import sin, cos, pi, sqrt, asin
+from math import sin, cos, pi, asin
 from tkinter import *
 
 laby_w, laby_h = 20, 12
@@ -96,26 +96,31 @@ canvas = Canvas(master, width = screen_w, height = screen_h + 68, bg = 'white')
 canvas.pack()
 
 def clean_screen():
+  global canvas
   canvas.delete('all')
 
 def draw_rect(x, y, w, h, color):
+  global canvas
   x += 1
   y += 1
   canvas.create_rectangle(x, y, x + w, y + h, fill = color, outline = '')
 
 def draw_line(x1, y1, x2, y2, color):
+  global canvas
   canvas.create_line(x1 + 1, y1 + 1, x2 + 1, y2 + 1, fill = color, width = 2.0)
 
 def draw_help():
+  global canvas
   help = 'change angle: [Shift+] Left/Right, change length: Up/Down, add/remove element: Enter/BackSpace, previous/next element: PgUp/PgDn, print code: P, exit: Esc'
   canvas.create_text(4, screen_h + 36, anchor = NW, text = help, fill = 'black')
 
 def draw_path():
-  global path
+  global canvas, path
   canvas.create_text(4, screen_h + 4, anchor = NW, text = '%s' % path[0:12], fill = 'black')
   canvas.create_text(4, screen_h + 20, anchor = NW, text = '%s' % path[12:24], fill = 'black')
 
 def draw_score(score):
+  global canvas
   canvas.create_text(4, screen_h + 52, anchor = NW, text = 'score: %f' % score, fill = 'black')
 
 def fix_angle(a):
@@ -183,5 +188,4 @@ def aller_selon(path):
 
 aller_selon(path)
 
-if __name__== "__main__":
-  master.mainloop()
+master.mainloop()