Quit function is not working in pygame
<p>I want the system to exit when I click the "x" on the window of pygame. I want to be able to call the <code>quit_game</code> function whenever I need to. So if the user does quit, it actually quits. I have tried <code>sys exit</code> and <code>pygame.quit()</code>, but I haven't been able to successfully implement those. Right now I just have the quit function built into the intro screen. I am using python 3.4.3. Here is the code.</p>

<pre><code>import math
import random
import time
import pygame
import sys
import glob
pygame.init()
move=0
FPS=60
blue=(0,0,255)
white=(255,255,255)
black=(0,0,0)
green=(0,155,0)
display_width=800
display_height=600
gamedisplay=pygame.display.set_mode((display_width,display_height))
pygame.display.set_caption('Stacker')
clock=pygame.time.Clock()
speed=2
smallfont=pygame.font.SysFont("Arial",int(display_width/32))
mediumfont=pygame.font.SysFont("Arial",int(display_width/16))
largefont=pygame.font.SysFont("Arial",int(display_width/10))
gamedisplay.fill(green)
block=display_height/12
pygame.display.update()
def quit_game():
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()
            quit()
def intro_screen():
    welcome_message = mediumfont.render(str("Welcome to Stacker!!!"), True,black)
    gamedisplay.blit(welcome_message,(display_width/4,display_height/40))
    how_to_play_1=smallfont.render(str("Your goal is to get to the major prize bar"),True,black)
    gamedisplay.blit(how_to_play_1,(display_width/3.619909502,display_height/2))
    how_to_play=smallfont.render(str("Press the space bar to stop the shape"),True,black)
    gamedisplay.blit(how_to_play,(display_width/3.48583878,display_height/(12/7)))
    quit_game()
    pygame.display.update()
def middle_block():
    pygame.draw.rect(gamedisplay, blue,(display_width/(32/15),display_height-block,block,block))
    pygame.display.update()
def left_block():
    pygame.draw.rect(gamedisplay, blue,(display_width/(32/13),display_height-block,block,block))
    pygame.display.update()
def right_block():
    pygame.draw.rect(gamedisplay, blue,(display_width/(32/17),display_height-block,block,block))
    pygame.display.update()
def major_screen():
    major_message = mediumfont.render(str("Major Prize Here!"), True,black)
    gamedisplay.blit(major_message,(display_width/(10/3),display_height/40))
    pygame.display.update()
intro_screen()
pygame.time.delay(8000)
gamedisplay.fill(green)
major_screen()
pygame.draw.rect(gamedisplay, blue,(display_width-display_width,display_height/8,display_width,display_height/60))
pygame.draw.rect(gamedisplay, blue,(display_width-display_width,display_height/2.4,display_width,display_height/60))
middle_block()
left_block()
right_block()
pygame.display.update()
</code></pre>