Python实现贪吃蛇小游戏

import random  
import pygame  
import sys  
from pygame.locals import *  
Snakespeed = 17  
Window_Width = 800  
Window_Height = 500  
Cell_Size = 20  
assert Window_Width % Cell_Size == 0, "Window width must be a multiple of cell size."  
assert Window_Height % Cell_Size == 0, "Window height must be a multiple of cell size."  
Cell_W = int(Window_Width / Cell_Size)  
Cell_H = int(Window_Height / Cell_Size)  
White = (255, 255, 255)  
Black = (0, 0, 0)  
Red = (255, 0, 0) 
Green = (0, 255, 0)  
DARKGreen = (0, 155, 0)  
DARKGRAY = (40, 40, 40)     
YELLOW = (255, 255, 0)  
Red_DARK = (150, 0, 0)  
BLUE = (0, 0, 255)  
BLUE_DARK = (0, 0, 150)  
BGCOLOR = Black  
UP = 'up'  
DOWN = 'down'      
LEFT = 'left'  
RIGHT = 'right'  
HEAD = 0  
def main():  
    global SnakespeedCLOCK, DISPLAYSURF, BASICFONT  

    pygame.init()  
    SnakespeedCLOCK = pygame.time.Clock()  
    DISPLAYSURF = pygame.display.set_mode((Window_Width, Window_Height))  
    BASICFONT = pygame.font.Font('freesansbold.ttf', 18)  
    pygame.display.set_caption('Snake')  
    showStartScreen()  
    while True:  
        runGame()  
        showGameOverScreen()  
def runGame():  
    startx = random.randint(5, Cell_W - 6)  
    starty = random.randint(5, Cell_H - 6)  
    wormCoords = [{'x': startx, 'y': starty},  
                  {'x': startx - 1, 'y': starty},  
                  {'x': startx - 2, 'y': starty}]  
    direction = RIGHT  
    apple = getRandomLocation()  
    while True:  
        for event in pygame.event.get():  
            if event.type == QUIT:  
                terminate()  
            elif event.type == KEYDOWN:  
                if (event.key == K_LEFT) and direction != RIGHT:  
                    direction = LEFT  
                elif (event.key == K_RIGHT) and direction != LEFT:  
                    direction = RIGHT  
                elif (event.key == K_UP) and direction != DOWN:  
                    direction = UP  
                elif (event.key == K_DOWN) and direction != UP:  
                    direction = DOWN