left  -- Command, one input.  Abbreviation: lt
     The input is a number, the number of degrees of  angle  through  which
     the turtle should turn counterclockwise.  This command does not change
     the position of the turtle, but merely its heading (the  direction  in
     which it points).  The turn will be only approximately correct for the
     floor turtle, because of mechanical errors.  For the  display  turtle,
     the  angle  will  be  perfectly reproducible, although it may not look
     quite right on the screen because of the difference  in  size  between
     horizontal  and vertical dots.  Nevertheless, a display turtle program
     will work in the sense that when the turtle is supposed to  return  to
     its starting point, it will do so.
