simple game in turtle

import turtle
import random

def up():
    t.setheading(90)
    t.forward(10)
    check_collision()

def down():
    t.setheading(270)
    t.forward(10)
    check_collision()

def left():
    t.setheading(180)
    t.forward(10)
    check_collision()

def right():
    t.setheading(0)
    t.forward(10)
    check_collision()

def check_collision():
    if (t.distance(apple) < 20):
        apple.goto(random.randint(-300, 300), random.randint(-300, 300))

t = turtle.Turtle()
t.shape("turtle")
t.speed(0)

apple = turtle.Turtle()
apple.shape("circle")
apple.color("red")
apple.penup()
apple.goto(random.randint(-300, 300), random.randint(-300, 300))

turtle.