Python Game Programming Tutorial: Snake Game Part 4

#Error? why does it leave blocks behind after the first one
# Simple Snake Game in Python 3 for beginners

import turtle
import time
import random

delay = 0.1

# Set up the screen
wn = turtle.Screen()
wn.title("Snake game")
wn.bgcolor("blue")
wn.setup(width=600, height=600)
wn.tracer(0)

#Snake head
head = turtle.Turtle()
head.speed(0)
head.shape("square")
head.color("pink")
head.penup()
head.goto(0,0)
head.direction = "stop"

# Snake food
food = turtle.Turtle()
food.speed(0)
food.shape("circle")
food.color("green")
food.penup()
food.goto(0,100)

segments = []



#Functions
def go_up():
    head.direction = "up"

def go_down():
    head.direction = "down"

def go_left():
    head.direction = "left"

def go_right():
    head.direction = "right"

#Functions
def move():
    if head.direction == "up":
        y = head.ycor()
        head.sety(y + 20)

    if head.direction == "down":
        y = head.ycor()
        head.sety(y + -20)

    if head.direction == "left":
        x = head.xcor()
        head.setx(x + -20)

    if head.direction == "right":
        x = head.xcor()
        head.setx(x + 20)

#keyboard bindings
wn.listen()
wn.onkeypress(go_up, "w")
wn.onkeypress(go_down, "s")
wn.onkeypress(go_left, "a")
wn.onkeypress(go_right, "d")



# Main game loop
while True:
    wn.update()
    # Check for a collision with the food
    if head.distance(food)<20:
        # Move food to random spot
        x = random.randint(-290,290)
        y = random.randint(-290, 290)
        food.goto(x, y)

        # Add a segment
        new_segment = turtle.Turtle()
        new_segment.speed(0)
        new_segment.shape("square")
        new_segment.color("pink")
        new_segment.penup()
        segments.append(new_segment)
        #print(segments)
    #Move the end segments first in reverse order
        for index in range(len(segments)-1, 0, -1):
            x = segments[index-1].xcor()
            y = segments[index-1].ycor()
            segments[index].goto(x, y)

    #Move segment 0 to where the head is
    if len(segments) > 0:
        x = head.xcor()
        y = head.ycor()
        segments[0].goto(x,y)


    move()

    time.sleep(delay)
wn.mainloop()