def is_valid_cell(cell_loc):
  """
  check whether a (x,y) coordinate is a valid cell on the game canvass
  """
  if cell_loc not in [ (0,0),  (0,1),  (0,2),  (0,5),  (0,6),  (0,7), \
                       (1,0),  (1,1),                  (1,6),  (1,7), \
                       (2,0),                                  (2,7), \
                      (11,0),                                 (11,7), \
                      (12,0), (12,1),                 (12,6), (12,7), \
                      (13,0), (13,1), (13,2), (13,5), (13,6), (13,7)]:
    return True
  else:
    return False