old_contents: import pygame, sys
  from pygame.locals import *
  import random
  
  WIDTH = 640
  HEIGHT = 480
  
  screen = pygame.display.set_mode((WIDTH, HEIGHT), 0, 32)
  pygame.display.set_caption("PongAI")
  clock = pygame.time.Clock()
  
  balls = []
  
  for _ in range(500):
  	ball = {
  		"x": random.randrange(0, WIDTH),
  		"y": random.randrange(0, HEIGHT),
  		"xvel": random.randrange(-10, 10),
  		"yvel": random.randrange(-10, 10),
  		"r": 10,
  		"color": (random.randrange(0, 0xFF), random.randrange(0, 0xFF), random.randrange(0, 0xFF))
  	}
  	balls.append(ball)
  
  while True:
  	for event in pygame.event.get():
  		if event.type == QUIT:
  			pygame.quit()
  			sys.exit()
  	screen.fill((0, 0, 0)) # clear the screen with black
  	
  	for ball in balls:
  		pygame.draw.rect(screen, ball["color"], (ball["x"]-ball["r"], ball["y"]-ball["r"], ball["r"]*2, ball["r"]*2), 0)
  		ball["x"] += ball["xvel"]
  		ball["y"] += ball["yvel"]
  		if (ball["xvel"] > 0 and ball["x"] + ball["r"] > WIDTH) or (ball["xvel"] < 0 and ball["x"] - ball["r"] < 0):
  			ball["xvel"] *= -1
  		if (ball["yvel"] > 0 and ball["y"] + ball["r"] > HEIGHT) or (ball["yvel"] < 0 and ball["y"] - ball["r"] < 0):
  			ball["yvel"] *= -1
  	
  	pygame.display.update()
  	clock.tick(60)
  
new_contents: import pygame, sys
  from pygame.locals import *
  import random
  
  WIDTH = 640
  HEIGHT = 480
  
  screen = pygame.display.set_mode((WIDTH, HEIGHT), 0, 32)
  pygame.display.set_caption("PongAI")
  clock = pygame.time.Clock()
  
  balls = []
  
  for _ in range(500):
  	ball = {
  		"x": random.randrange(0, WIDTH),
  		"y": random.randrange(0, HEIGHT),
  		"xvel": random.randrange(-4, 4),
  		"yvel": random.randrange(-4, 4),
  		"r": 10,
  		"color": (random.randrange(0, 0xFF), random.randrange(0, 0xFF), random.randrange(0, 0xFF))
  	}
  	balls.append(ball)
  
  bat = {
  	"x": 30,
  	"y": HEIGHT/2,
  	"width": 10, # actually, half the width and height
  	"height": 50,
  	"color": (0xFF, 0xFF, 0xFF)
  }
  
  while True:
  	for event in pygame.event.get():
  		if event.type == QUIT:
  			pygame.quit()
  			sys.exit()
  	screen.fill((0, 0, 0)) # clear the screen with black
  	
  	for ball in balls:
  		pygame.draw.rect(screen, ball["color"], (ball["x"]-ball["r"], ball["y"]-ball["r"], ball["r"]*2, ball["r"]*2), 0)
  		ball["x"] += ball["xvel"]
  		ball["y"] += ball["yvel"]
  		if (ball["xvel"] > 0 and ball["x"] + ball["r"] > WIDTH) or (ball["xvel"] < 0 and ball["x"] - ball["r"] < 0):
  			ball["xvel"] *= -1
  		if (ball["yvel"] > 0 and ball["y"] + ball["r"] > HEIGHT) or (ball["yvel"] < 0 and ball["y"] - ball["r"] < 0):
  			ball["yvel"] *= -1
  	
  	pygame.draw.rect(screen, bat["color"], (bat["x"]-bat["width"], bat["y"]-bat["height"], bat["width"]*2, bat["height"]*2), 0)
  	
  	pygame.display.update()
  	clock.tick(60)
  
subject: add bat