Pygame入門 ブロック崩しのパドルをマウスで動かす

import pygame
import sys

SCREEN = pygame.Rect(0, 0, 400, 400)
FPS = 30

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

PADDLE_WIDTH = 60
PADDLE_HEIGHT = 20
PADDLE_POS_Y = SCREEN.bottom - PADDLE_HEIGHT * 2

pygame.init()
clock = pygame.time.Clock()
screen = pygame.display.set_mode(SCREEN.size)
paddle = pygame.Surface((PADDLE_WIDTH, PADDLE_HEIGHT))
paddle.fill(GREEN)

while True:
    screen.fill(WHITE)

    PADDLE_POS_X = pygame.mouse.get_pos()[0]
    if PADDLE_POS_X > (SCREEN.right - PADDLE_WIDTH):
        PADDLE_POS_X = SCREEN.right - PADDLE_WIDTH
    screen.blit(paddle, (PADDLE_POS_X, PADDLE_POS_Y))

    pygame.display.update()
    clock.tick(FPS)

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()