enter code here
import pygame
import random
import sys

pygame.init()

white = (255,255,255)
black = (0,0,0)
red = (255,0,0)
green = (0,155,0)

display_width = 800
display_height = 600

gameDisplay = pygame.display.set_mode((display_width,display_height))
pygame.display.set_caption("Snake(alpha edition)")

movement = 10
block_size = 10
FPS = 22

font = pygame.font.SysFont(None, 25)

def snake(block_size, snakelist):
    for xny in snakelist:
        pygame.draw.rect(gameDisplay, green, [xny[0], xny[1], block_size, block_size])


def gameover_msg(msg,color):
    screen_text = font.render(msg, True, color)
    gameDisplay.blit(screen_text, [display_width/2, display_height/2])


def gameLoop():
    gameExit = False
    gameOver = False
    pos_x = display_width/2
    pos_y = display_height/2
    pos_x_change = 0
    pos_y_change = 0
    clock = pygame.time.Clock()
    randAppleX = round(random.randrange(0, display_width-block_size)/10.0)*10.0
    randAppleY = round(random.randrange(0, display_height-block_size)/10.0)*10.0
    snakelist = []
    snakelength = 1

    while not gameExit:

        while gameOver == True:
            gameDisplay.fill(white)
            gameover_msg("Game over, press R to play again or Q to quit", red)
            pygame.display.update()

            for event in pygame.event.get():
                if event.type == pygame.KEYDOWN:
                    if event.key == pygame.K_q:
                        gameExit = True
                        gameOver = False
                    if event.key == pygame.K_r:
                        gameLoop()




        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                gameExit = True
            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_LEFT:
                    pos_x_change = -movement
                    pos_y_change = 0
                elif event.key == pygame.K_RIGHT:
                    pos_x_change = movement
                    pos_y_change = 0
                elif event.key == pygame.K_UP:
                    pos_y_change = -movement
                    pos_x_change = 0
                elif event.key == pygame.K_DOWN:
                    pos_y_change = movement
                    pos_x_change = 0

            if pos_x >= display_width or pos_x < 0 or pos_y >= display_height or pos_y < 0:
                gameOver = True


            if pos_x == randAppleX and pos_y == randAppleY:
                randAppleX = round(random.randrange(0, display_width-block_size)/10.0)*10.0
                randAppleY = round(random.randrange(0, display_height-block_size)/10.0)*10.0
                snakelength += 1


        pos_x += pos_x_change
        pos_y += pos_y_change

        gameDisplay.fill(white)
        pygame.draw.rect(gameDisplay, red, [randAppleX, randAppleY, block_size, block_size])

        snakehead = []
        snakehead.append(pos_x)
        snakehead.append(pos_y)
        snakelist.append(snakehead)

        if len(snakelist) > snakelength:
            del snakelist[0]

        if snakehead in snakelist[:-1]:
            if not snakehead == snakelist[0]:
                continue
            gameOver = True


        snake(block_size, snakelist)
        pygame.display.update()
        clock.tick(FPS)

    pygame.quit()
    sys.exit()
    quit()


gameLoop()