Slither Game in PyGame

CODE:

import pygame,sys
import time
import random
pygame.init()

white = (255,255,255)
black = (100,0,0)
red = (255,0,0)
window_width = 800
window_height = 600

gameDisplay = pygame.display.set_mode((window_width,window_height))

pygame.display.set_caption('slither')

clock = pygame.time.Clock()

FPS = 5

blockSize = 20

noPixel = 0

'''
sizeGrd = window_width // blockSize

row = 0

col = 0

for nextline in range(sizeGrd):
'''

def myquit():
    ''' Self explanatory '''
    pygame.quit()
    sys.exit(0)

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

def drawGrid():

	sizeGrd = window_width // blockSize

def snake(blockSize, snakelist):

    #x = 250 - (segment_width + segment_margin) * i

    for size in snakelist:

        pygame.draw.rect(gameDisplay, black,[size[0]+5,size[1],blockSize,blockSize],2)

def message_to_screen(msg, color):

    screen_text = font.render(msg, True, color)

    gameDisplay.blit(screen_text, [window_width/2, window_height/2])

def gameLoop():

    gameExit = False

    gameOver = False

    lead_x = window_width/2

    lead_y = window_height/2

    change_pixels_of_x = 0

    change_pixels_of_y = 0

    snakelist = []

    snakeLength = 1

    randomAppleX = round(random.randrange(0, window_width-blockSize)/10.0)*10.0

    randomAppleY = round(random.randrange(0, window_height-blockSize)/10.0)*10.0
    
    while not gameExit:
    
        while gameOver == True:

            gameDisplay.fill(white)

            message_to_screen("Game over, press c to play again or Q to quit", red)

            pygame.display.update()

            for event in pygame.event.get():

                if event.type == pygame.QUIT:

                    gameOver = False

                    gameExit = True
                    
                if event.type == pygame.KEYDOWN:

                    if event.key == pygame.K_q:

                        gameExit = True

                        gameOver = False

                    if event.key == pygame.K_c:

                        gameLoop()
                        
        for event in pygame.event.get():

            if event.type == pygame.QUIT:

                gameExit = True

            if event.type == pygame.KEYDOWN:

                if event.key == pygame.K_ESCAPE:

                    myquit()

                leftArrow = event.key == pygame.K_LEFT

                rightArrow = event.key == pygame.K_RIGHT

                upArrow = event.key == pygame.K_UP

                downArrow = event.key == pygame.K_DOWN

                if leftArrow:

                    change_pixels_of_x = -blockSize

                    change_pixels_of_y = noPixel

                elif rightArrow:

                    change_pixels_of_x = blockSize

                    change_pixels_of_y = noPixel

                elif upArrow:

                    change_pixels_of_y = -blockSize

                    change_pixels_of_x = noPixel

                elif downArrow:

                    change_pixels_of_y = blockSize

                    change_pixels_of_x = noPixel

            if lead_x >= window_width or lead_x < 0 or lead_y >= window_height or lead_y < 0:

                gameOver = True
                
        lead_x += change_pixels_of_x

        lead_y += change_pixels_of_y
        
        gameDisplay.fill(white)
        
        AppleThickness = 20
        print([int(randomAppleX),int(randomAppleY),AppleThickness,AppleThickness])

        pygame.draw.rect(gameDisplay, red, [randomAppleX,randomAppleY,AppleThickness,AppleThickness])

        allspriteslist = []

        allspriteslist.append(lead_x)

        allspriteslist.append(lead_y)

        snakelist.append(allspriteslist)

        if len(snakelist) > snakeLength:

            del snakelist[0]
            
        for eachSegment in snakelist [:-1]:

            if eachSegment == allspriteslist:

                gameOver = True
                
        snake(blockSize, snakelist)

        pygame.display.update()
        
        if lead_x >= randomAppleX and lead_x <= randomAppleX + AppleThickness:

            if lead_y >= randomAppleY and lead_y <= randomAppleY + AppleThickness:

                randomAppleX = round(random.randrange(0, window_width-blockSize)/10.0)*10.0

                randomAppleY = round(random.randrange(0, window_height-blockSize)/10.0)*10.0

                snakeLength += 1 
        clock.tick(FPS)

    pygame.quit()

    quit()

gameLoop()