pygame是用来写2D游戏的。
实现斜线运动，无非是在x和y两个方向上分运动的合成。x方向上的运动，当撞到边界的时候取相反速度就好了。
这里是用网球王子中的图片，以及一个网球实现，效果截图：
注意看，那个方块形状的网球是会动的，撞到边界就反弹，时刻匀速（这情况太理想了。。。）
代码：
# coding:utf-8
bgimg = 'teni.jpg'
spimg = 'ball.jpg'
import pygame
from pygame.locals import *
from sys import exit
pygame.init()
screen = pygame.display.set_mode((640, 480), 0, 32)
bg = pygame.image.load(bgimg).convert()
sp = pygame.image.load(spimg).convert_alpha()
clock = pygame.time.Clock()
x, y =100., 100.
speed_x, speed_y = 133., 170.
while True:
for event in pygame.event.get():
if event.type == QUIT:
exit()
screen.blit(bg, (0, 0))
screen.blit(sp, (x, y))
time_passed = clock.tick(30) # 设定最大FPS不超过30
# FPS：Frame per second
time_passed_seconds = time_passed / 1000.0
x += speed_x * time_passed_seconds
y += speed_y * time_passed_seconds
if x > 640 - sp.get_width():
speed_x = -speed_x
x = 640 - sp.get_width()
elif x < 0:
speed_x = - speed_x
x = 0.
if y > 480 - sp.get_height():
speed_y = -speed_y
y = 480 - sp.get_height()
elif y < 0:
speed_y = -speed_y
y = 0
pygame.display.update()
