Замена изображений в pygame

Разобрался со "змейкой" по туториалам, вопрос по поводу замены изображений во время игры. Допустим, я хочу чтобы одно изображение круга становилось другим при достижении змейкой определенной длины (например, 5), при этом, если это возможно, чтобы сама змейка принимала эти изображения "в себя", то есть блоки змейки становились этими самыми изображениями.

import pygame
from pygame.locals import *
import time
import random

SIZE = 40


class Circle:
    def __init__(self, parent_screen):
        self.parent_screen = parent_screen
        self.image = pygame.image.load("objects/circle1.png").convert_alpha()
        self.image = pygame.transform.scale(self.image, (30, 30))
        self.x = 120
        self.y = 120

    def draw(self):
        self.parent_screen.blit(self.image, (self.x, self.y))
        pygame.display.flip()

    def move(self):
        self.x = random.randint(1, 22) * SIZE
        self.y = random.randint(1, 16) * SIZE


class Snake:
    def __init__(self, parent_screen):
        self.parent_screen = parent_screen
        self.image = pygame.image.load("objects/block1.jpg").convert()
        self.image = pygame.transform.scale(self.image, (30, 30))
        self.direction = 'down'

        self.length = 1
        self.x = [40]
        self.y = [40]

    def move_left(self):
        self.direction = 'left'

    def move_right(self):
        self.direction = 'right'

    def move_up(self):
        self.direction = 'up'

    def move_down(self):
        self.direction = 'down'

    def walk(self):
        # update body
        for i in range(self.length - 1, 0, -1):
            self.x[i] = self.x[i - 1]
            self.y[i] = self.y[i - 1]

        # update head
        if self.direction == 'left':
            self.x[0] -= SIZE
        if self.direction == 'right':
            self.x[0] += SIZE
        if self.direction == 'up':
            self.y[0] -= SIZE
        if self.direction == 'down':
            self.y[0] += SIZE

        self.draw()

    def draw(self):
        for i in range(self.length):
            self.parent_screen.blit(self.image, (self.x[i], self.y[i]))

        pygame.display.flip()

    def increase_length(self):
        self.length += 1
        self.x.append(-1)
        self.y.append(-1)


class Game:
    def __init__(self):
        pygame.init()

        self.surface = pygame.display.set_mode((1000, 800))
        self.snake = Snake(self.surface)
        self.snake.draw()
        self.apple = Circle(self.surface)
        self.apple.draw()

    def reset(self):
        self.snake = Snake(self.surface)
        self.apple = Apple(self.surface)

    def is_collision(self, x1, y1, x2, y2):
        if x1 >= x2 and x1 < x2 + SIZE:
            if y1 >= y2 and y1 < y2 + SIZE:
                return True
        return False

    def render_background(self):
        bg = pygame.image.load("objects/Y7If5J.jpg").convert()
        self.surface.blit(bg, (0, 0))

    def play(self):
        self.render_background()
        self.snake.walk()
        self.apple.draw()
        self.display_score()
        pygame.display.flip()

        for i in range(self.snake.length):
            if self.is_collision(self.snake.x[i], self.snake.y[i], self.apple.x, self.apple.y):
                self.snake.increase_length()
                self.apple.move()

        # snake colliding with itself
        for i in range(3, self.snake.length):
            if self.is_collision(self.snake.x[0], self.snake.y[0], self.snake.x[i], self.snake.y[i]):
                raise "Collision Occurred"

        # snake colliding with the boundries of the window
        if not (0 <= self.snake.x[0] <= 1000 and 0 <= self.snake.y[0] <= 800):
            raise "Hit the boundry error"

    def display_score(self):
        font = pygame.font.SysFont('arial', 30)
        score = font.render(f"Score: {self.snake.length}", True, (200, 200, 200))
        self.surface.blit(score, (850, 10))

    def show_game_over(self):
        self.render_background()
        font = pygame.font.SysFont('arial', 30)
        line1 = font.render(f"Game is over! Your score is {self.snake.length}", True, (255, 255, 255))
        self.surface.blit(line1, (200, 300))
        line2 = font.render("To play again press Enter. To exit press Escape!", True, (255, 255, 255))
        self.surface.blit(line2, (200, 350))
        pygame.display.flip()

    def run(self):
        running = True
        pause = False

        while running:
            for event in pygame.event.get():
                if event.type == KEYDOWN:
                    if event.key == K_ESCAPE:
                        running = False

                    if event.key == K_RETURN:
                        pause = False

                    if not pause:
                        if event.key == K_LEFT:
                            self.snake.move_left()

                        if event.key == K_RIGHT:
                            self.snake.move_right()

                        if event.key == K_UP:
                            self.snake.move_up()

                        if event.key == K_DOWN:
                            self.snake.move_down()

                elif event.type == QUIT:
                    running = False
            try:

                if not pause:
                    self.play()

            except Exception as e:
                self.show_game_over()
                pause = True
                self.reset()

            time.sleep(.1)


if __name__ == '__main__':
    game = Game()
    game.run()