使用blit方法创建动态文本

我正在创建一个基本游戏，黑色方块在屏幕上移动 . 还有另外两个正方形，绿色正方形和红色正方形 . 当黑色方块与红色方块碰撞时，它退出程序，当它与绿色方块碰撞时，它会加到你的点计数器上 . 我有红色方块部分，但我在使用精灵和类创建动态文本时遇到问题 . 我问过的上一个问题的某个人告诉我，我应该将分数搞砸到屏幕上，然后每当广场与绿色方块相撞时重新加入它 . 但是，我不知道如何正确地做到这一点 . 这是我的代码：

import os, sys
import pygame
from pygame.locals import *

pygame.init()
mainClock = pygame.time.Clock()

WINDOWWIDTH = 1000
WINDOWHEIGHT = 700
windowSurface = pygame.display.set_mode((WINDOWWIDTH, WINDOWHEIGHT), 0, 32)
pygame.display.set_caption("Avoid!")

BLACK = (0, 0, 0)
RED = (255, 0, 0)
WHITE = (255, 255, 255)
GREEN = (0, 255, 0)

player = pygame.Rect(500, 300, 40, 40)
playerImage = pygame.Surface((40, 40))

enemy = pygame.Rect(300, 400, 20, 20)
enemyImage = pygame.Surface((20, 20))
enemyImage.fill((RED))

food = pygame.Rect(300, 500 , 20, 20)
foodImage = pygame.Surface((20, 20))
foodImage.fill((GREEN))

class Score(pygame.sprite.Sprite):
    """A sprite for the score."""

    def __init__(self, xy):
        pygame.sprite.Sprite.__init__(self)
        self.xy = xy    # save xy -- will center our rect on it when we change the score
        self.font = pygame.font.Font(None, 50)  # load the default font, size 50
        self.color = (BLACK)         # our font color in rgb
        self.score = 0  # start at zero
        self.reRender() # generate the image

    def update(self):
        pass

    def add(self, points):
        """Adds the given number of points to the score."""
        if player.colliderect(food):
            my_score.score += points
        self.reRender()

    def reset(self):
        """Resets the scores to zero."""
        self.score = 0
        self.reRender()

    def reRender(self):
        """Updates the score. Renders a new image and re-centers at the initial coordinates."""
        self.image = self.font.render("%d"%(self.score), True, self.color)
        self.rect = self.image.get_rect()
        self.rect.center = self.xy

my_score = Score((75, 575))
print my_score.score

font = pygame.font.Font(None, 36)
text = font.render("%d" % (my_score.score), 1, (10, 10, 10))
textpos = text.get_rect(centerx=windowSurface.get_width()/2)

moveLeft = False
moveRight = False
moveUp = False
moveDown = False

MOVESPEED = 6

while True:
    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()
        if event.type == KEYDOWN:
            if event.key == K_LEFT:
                moveRight = False
                moveLeft = True
            if event.key == K_RIGHT:
                moveLeft = False
                moveRight = True
            if event.key == K_UP:
                moveDown = False
                moveUp = True
            if event.key == K_DOWN:
                moveUp = False
                moveDown = True
        if event.type == KEYUP:
            if event.key == K_ESCAPE:
                pygame.quit()
                sys.exit()
            if event.key == K_LEFT:
                moveRight = False
                moveLeft = True
            if event.key == K_RIGHT:
                moveLeft = False
                moveRight = True
            if event.key == K_UP:
                moveDown = False
                moveUp = True
            if event.key == K_DOWN:
                moveUp = False
                moveDown = True

    windowSurface.fill(WHITE)

    if moveDown and player.bottom < WINDOWHEIGHT:
        player.top += MOVESPEED
    if moveUp and player.top > 0:
        player.top -= MOVESPEED
    if moveLeft and player.left > 0:
        player.left -= MOVESPEED
    if moveRight and player.right < WINDOWWIDTH:
        player.right +=MOVESPEED

    if player.colliderect(enemy):
        pygame.quit()
        sys.exit()

    windowSurface.blit(playerImage, player)
    windowSurface.blit(enemyImage, enemy)
    windowSurface.blit(foodImage, food)
    windowSurface.blit(text, textpos)

    score = Score((75, 575))

    pygame.display.update()
    mainClock.tick(40)

我是否将windowSurface.blit（text，textpos）放入Score类的add函数中？一旦大方块接触到小绿色广场，我该如何提高分数？