# -*- coding: utf-8 -*-
import pygame
import random
 
# 初始化pygame
pygame.init()
  
# 根據背景圖片的大小，設定螢幕長寬
SIZE = (1364, 569)
 
screen = pygame.display.set_mode(SIZE)
pygame.display.set_caption("Snow Animation")
bg = pygame.image.load('snow.jpg')

# 雪花列表
snow_list = []
 
# 初始化雪花：[x座標, y座標, x軸速度, y軸速度]
for i in range(200):
    x = random.randrange(0, SIZE[0])
    y = random.randrange(0, SIZE[1])
    sx = random.randint(-1, 1)
    sy = random.randint(3, 6)
    snow_list.append([x, y, sx, sy])
 
clock = pygame.time.Clock()
 
# 遊戲主迴圈
done = False
while not done:
    # 訊息事件迴圈，判斷退出
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            done = True
 
    # 黑背景/圖片背景
    # screen.fill((0, 0, 0))
    screen.blit(bg, (0, 0))

    # 雪花列表迴圈
    for i in range(len(snow_list)):
        # 繪製雪花，顏色、位置、大小
        pygame.draw.circle(screen, (255, 255, 255), snow_list[i][:2], snow_list[i][3]-3)
 
        # 移動雪花位置（下一次迴圈起效）
        snow_list[i][0] += snow_list[i][2]
        snow_list[i][1] += snow_list[i][3]
 
        # 如果雪花落出螢幕，重設位置
        if snow_list[i][1] > SIZE[1]:
            snow_list[i][1] = random.randrange(-50, -10)
            snow_list[i][0] = random.randrange(0, SIZE[0])
 
    # 重新整理螢幕
    pygame.display.flip()
    clock.tick(20)

# 退出 
pygame.quit()