Hello, please help me out with this, the game start page is not working 

import pygame
import random
      
pygame.init()
cream = (255,235,205)
black = (0,0,0)
red = (255,0,0)

display_width = 800
display_height = 600
FPS = 15

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


clock = pygame.time.Clock()

block_size = 10

font = pygame.font.SysFont(None,25)
snakefont = pygame.font.SysFont(None,50)
def snake(block_size, snakelist):

    for XnY in snakelist:
        pygame.draw.rect(gameDisplay, black, [XnY[0],XnY[1], block_size, block_size]) 

    

# Creating the text insert function
def message(msg,color,y_location=0):
    text_screen = font.render(msg,True,color)
    text_rect = text_screen.get_rect()
    text_rect.center = (display_width/2),(display_height/2)+y_location
    gameDisplay.blit(text_screen,text_rect)

def start(msg,color,y_location=0):
    text_screen = snakefont.render(msg,True,color)
    text_rect = text_screen.get_rect()
    text_rect.center = (display_width/2),(display_height/2)+y_location
    gameDisplay.blit(text_screen,text_rect)
    
#for the score
def score(scr,color):
    a = 0
    score_text = font.render(scr + str(a) ,True,color)
    gameDisplay.blit(score_text, [5,5])

def gameintro():
    intro = True
    while intro == True:
        gameDisplay.fill(black)
        start("My Snake Game", black, -50)
        message("Press C or Q", black, 50)
        pygame.display.update
        clock.tick(15)                     

    
#gameloop function
def gameLoop():
    gameExit = False
    gameOver =  False

    lead_x = display_width / 2
    lead_y = display_height / 2
    snakelist = []
    snakelength = 1
    a = 0
    xchange = 0
    ychange = 0

    randAppleX = round(random.randrange(0,display_width-block_size)/10)*10
    randAppleY = round(random.randrange(0,display_height-block_size)/10)*10 
        
    while not gameExit:
        
        
#loop for game over and choices
        while gameOver == True:
            
            gameDisplay.fill(cream)
            start("Game Over", black, -50)
            message("Press C or Q", black, 50)
            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_c:
                        gameLoop()
                    if event.key == pygame.K_q:
                        gameOver = False
                        gameExit = True

        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                gameExit = True
            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_LEFT:
                    xchange = -block_size
                    ychange = 0
                elif event.key == pygame.K_RIGHT:
                    xchange = block_size
                    ychange = 0
                elif event.key == pygame.K_UP:
                    ychange = -block_size
                    xchange = 0
                elif event.key == pygame.K_DOWN:
                    ychange = block_size
                    xchange = 0
        # states the boundaries are the limits
        if lead_x >= display_width or lead_x < 0 or lead_y >= display_height or lead_y < 0:
            gameOver = True 


        lead_x += xchange
        lead_y += ychange
        gameDisplay.fill(cream)
        pygame.draw.rect(gameDisplay, red, [randAppleX, randAppleY, block_size, block_size])
 #snake length
 
        snakehead = []
        snakehead.append(lead_x)
        snakehead.append(lead_y)
        snakelist.append(snakehead)
        if len(snakelist) > snakelength:
            del snakelist [0]
#end game when the snake touches its body
        for segment in snakelist[:-1]:
            if segment == snakehead:
                gameOver = True
                
        
        snake(block_size, snakelist)
        score("Score: "+ str(a), black)

        pygame.display.update()
 # States what happens when the apple and the snake collide   
        if lead_x == randAppleX and lead_y == randAppleY:
            randAppleX = round(random.randrange(0,display_width-block_size)/10)*10
            randAppleY = round(random.randrange(0,display_height-block_size)/10)*10
            snakelength += 1
            a += 1
              
        clock.tick(FPS)

    pygame.quit()
    quit()
    
gameintro()
gameLoop()