text: from turtle import Turtle
  STARTING_POSITIONS = [(0, 0), (-20, 0), (-40, 0)]
  MOVE_DISTANCE = 20
  UP = 90
  DOWN = 270
  LEFT = 180
  RIGHT = 0
  
  
  class Snake:
  
      def __init__(self):
          self.segments = []
          self.create_snake()
          self.head = self.segments[0]
  
      def create_snake(self):
          for position in STARTING_POSITIONS:
              self.add_segment(position)
  
      def add_segment(self, position):
          new_segment = Turtle("square")
          new_segment.color("yellow")
          new_segment.penup()
          new_segment.goto(position)
          self.segments.append(new_segment)
  
      def reset(self):
          for seg in self.segments:
              seg.goto(1000,1000)
          self.segments.clear()
          self.create_snake()
          self.head=self.segments[0]
  
      def extend(self):
          self.add_segment(self.segments[-1].position())
  
      def move(self):
          for seg_num in range(len(self.segments) - 1, 0, -1):
              new_x = self.segments[seg_num - 1].xcor()
              new_y = self.segments[seg_num - 1].ycor()
              self.segments[seg_num].goto(new_x, new_y)
          self.head.forward(MOVE_DISTANCE)
  
      def up(self):
          if self.head.heading() != DOWN:
              self.head.setheading(UP)
  
      def down(self):
          if self.head.heading() != UP:
              self.head.setheading(DOWN)
  
      def left(self):
          if self.head.heading() != RIGHT:
              self.head.setheading(LEFT)
  
      def right(self):
          if self.head.heading() != LEFT:
              self.head.setheading(RIGHT)
  