Python Animations不适用于Fangame Zelda

Question

我的代码没有按照我想要的方式工作。我试图在移动时将我的var编程为面向方向。它搞砸了。请尽力帮助我。谢谢。当我试图向上移动时，动画不显示，但是当我向上和向右移动时，它就会起作用。然而，这是唯一一个以任何方式工作的人.......

这是我的代码：

import pygame
from pygame.locals import *
a = 20
# 2 - Initialize the game
pygame.init()
width, height = 720,540
keys = [False, False, False, False]
playerpos=[100,100]
screen=pygame.display.set_mode((width, height))
pygame.display.set_caption("Zelda")
Background = (245,204,153)
# 3 - Load images
down1 = pygame.image.load('link_down1.png')
down2 = pygame.image.load('link_down2.png')
up1   = pygame.image.load('link_up1.png')
up2   = pygame.image.load('link_up2.png')
left1 = pygame.image.load('link_left1.png')
left2 = pygame.image.load('link_left2.png')
player = pygame.image.load("resources/images/link.png")
tree =    pygame.image.load("resources/images/tree.png")
right = pygame.transform.flip(left1,True,False)

# 4 - keep looping through
while 1:
    # 5 - clear the screen before drawing it again
    screen.fill(Background)
    # 6 - draw the screen elements
    screen.blit(player, playerpos)
    screen.blit(tree, (0,0))
    screen.blit(tree, (0,20))
    screen.blit(tree, (0,40))
    screen.blit(tree, (20,0))
    screen.blit(tree, (20,20))
    screen.blit(tree, (20,40))
    screen.blit(tree, (40,0))
    screen.blit(tree, (40,20))
    screen.blit(tree, (40,40))
    pygame.display.flip()
    # 7 - loop through the events
    for event in pygame.event.get():
      if event.type == pygame.KEYDOWN:
            if event.key==K_w:
                keys[0]=True
            elif event.key==K_a:
                keys[1]=True
            elif event.key==K_s:
                keys[2]=True
            elif event.key==K_d:
                keys[3]=True
      if event.type == pygame.KEYUP:
            if event.key==pygame.K_w:
                keys[0]=False
            elif event.key==pygame.K_a:
                keys[1]=False
            elif event.key==pygame.K_s:
                keys[2]=False
            elif event.key==pygame.K_d:
                keys[3]=False
        # check if the event is the X button 
      if event.type==pygame.QUIT:
            # if it is quit the game
            pygame.quit() 
            exit(0)
        # 8 - Move player
    if keys[0]:
        screen.blit(up1, playerpos)
        playerpos[1]-=0.2
        screen.fill(Background)
        screen.blit(up1,playerpos)
        screen.blit(tree, (0,0))
        screen.blit(tree, (0,20))
        screen.blit(tree, (0,40))
        screen.blit(tree, (20,0))
        screen.blit(tree, (20,20))
        screen.blit(tree, (20,40))
        screen.blit(tree, (40,0))
        screen.blit(tree, (40,20))
        screen.blit(tree, (40,40))
    elif keys[2]:
      screen.blit(down1, playerpos)
      playerpos[1]+=0.2
      screen.fill(Background)
      screen.blit(up1,playerpos)
      screen.blit(tree, (0,0))
      screen.blit(tree, (0,20))
      screen.blit(tree, (0,40))
      screen.blit(tree, (20,0))
      screen.blit(tree, (20,20))
      screen.blit(tree, (20,40))
      screen.blit(tree, (40,0))
      screen.blit(tree, (40,20))
      screen.blit(tree, (40,40))
    if keys[1]:
        screen.blit(left1, playerpos)
        playerpos[0]-=0.2
        screen.fill(Background)
        screen.blit(up1,playerpos)
        screen.blit(tree, (0,0))
        screen.blit(tree, (0,20))
        screen.blit(tree, (0,40))
        screen.blit(tree, (20,0))
        screen.blit(tree, (20,20))
        screen.blit(tree, (20,40))
        screen.blit(tree, (40,0))
        screen.blit(tree, (40,20))
        screen.blit(tree, (40,40))        
    elif keys[3]:
      screen.blit(right, playerpos)
      playerpos[0]+=0.2
      screen.fill(Background)
      screen.blit(up1,playerpos)
      screen.blit(tree, (0,0))
      screen.blit(tree, (0,20))
      screen.blit(tree, (0,40))
      screen.blit(tree, (20,0))
      screen.blit(tree, (20,20))
      screen.blit(tree, (20,40))
      screen.blit(tree, (40,0))
      screen.blit(tree, (40,20))
      screen.blit(tree, (40,40))
    #9
      pygame.display.flip()