在Python中pgzero怎么给打砖块游戏增加关卡

要给打砖块游戏增加关卡，可以通过以下步骤实现：

1. 定义每个关卡的砖块布局和难度等级。
2. 在游戏循环中添加关卡切换的逻辑，例如在当前关卡的所有砖块被消除后，切换到下一个关卡。
3. 在游戏开始时加载第一关的砖块布局和难度等级。

以下是一个示例代码，实现了两个关卡的打砖块游戏：

import pgzrun
import random

WIDTH = 400
HEIGHT = 600
BRICK_WIDTH = 50
BRICK_HEIGHT = 20
BRICK_ROWS = 4
BRICK_COLS = 8

def make_bricks():
    bricks = []
    for row in range(BRICK_ROWS):
        for col in range(BRICK_COLS):
            brick = Actor('brick', pos=(col * BRICK_WIDTH + BRICK_WIDTH / 2, row * BRICK_HEIGHT + 100))
            brick.hp = 1 + current_level
            bricks.append(brick)
    return bricks

def draw():
    screen.clear()
    for brick in bricks:
        brick.draw()
    ball.draw()
    paddle.draw()
    screen.draw.text(f"Level: {current_level}", midtop=(WIDTH/2, 10), fontsize=30, color="white")

def update():
    global ball_speed, bricks, current_level
    ball.x += ball_speed[0]
    ball.y += ball_speed[1]
    if ball.left < 0 or ball.right > WIDTH:
        ball_speed[0] = -ball_speed[0]
    if ball.top < 0:
        ball_speed[1] = -ball_speed[1]
    if ball.bottom > HEIGHT:
        ball_speed = [5, 5]
        ball.pos = (WIDTH/2, HEIGHT/2)
        current_level = 1
        bricks = make_bricks()
    if ball.colliderect(paddle):
        ball_speed[1] = -ball_speed[1]
        ball_speed[0] = (ball.x - paddle.x) / 8
    for brick in bricks:
        if ball.colliderect(brick):
            ball_speed[1] = -ball_speed[1]
            brick.hp -= 1
            if brick.hp == 0:
                bricks.remove(brick)
    if len(bricks) == 0:
        current_level += 1
        ball_speed = [5 + current_level, 5 + current_level]
        bricks = make_bricks()

def on_key_down(key):
    if key == keys.LEFT:
        paddle.x -= 50
    elif key == keys.RIGHT:
        paddle.x += 50

bricks = make_bricks()
paddle = Actor('paddle', pos=(WIDTH/2, HEIGHT-50))
ball = Actor('ball', pos=(WIDTH/2, HEIGHT/2))
ball_speed = [5, 5]
current_level = 1

pgzrun.go()

在这个示例代码中，我们定义了`make_bricks`函数来生成每个关卡的砖块布局和难度等级。在`update`函数中，我们添加了关卡切换的逻辑，当当前关卡的所有砖块被消除后，切换到下一个关卡。在游戏开始时，我们加载第一关的砖块布局和难度等级。