洞穴里的软泥怪

本课属于 Coddy Pygame 学习旅程的“游戏世界”单元。第 33 课，共 36 课。

两个 blob 在洞穴地面上巡逻。下面是“巡逻的敌人”一课中的 Blob 类及其行走动画：它会在墙壁和悬崖边缘处转向，并交替显示两种姿势。

class Blob(pygame.sprite.Sprite):
    def __init__(self, midbottom):
        super().__init__()
        self.frames = [blob_img, blob_walk_img]
        self.image = blob_img
        self.rect = pygame.Rect(0, 0, 30, 26)
        self.rect.midbottom = midbottom
        self.direction = 1
        self.timer = 0

    def update(self):
        self.timer += 1
        self.image = self.frames[self.timer // 10 % 2]
        self.rect.x += self.direction
        if self.direction > 0:
            ahead = self.rect.right
        else:
            ahead = self.rect.left - 1
        hit_wall = any(self.rect.colliderect(wall) for wall in walls)
        ground_ahead = any(wall.collidepoint(ahead, self.rect.bottom) for wall in walls)
        if hit_wall or not ground_ahead:
            self.rect.x -= self.direction
            self.direction = -self.direction

地图中的每个 E 都会在对应的地块上添加一个 blob。每一帧都先更新整个组，再检测每个 blob 是否与玩家碰撞。踩中 blob 会将其移除，并让玩家弹起；其他任何接触都是危险的，因此会像碰到尖刺一样将 hurt 设为真：

blobs.update()
for blob in blobs:
    if player.colliderect(blob.rect):
        if vel_y > 0 and player.bottom < blob.rect.centery:
            blob.kill()
            vel_y = -8
        else:
            hurt = True

通过摄像机绘制每个 blob，让图像的底部中心对齐其 Rect 的底部中心：

spot = blob.image.get_rect(midbottom=(blob.rect.centerx - camera_x, blob.rect.bottom))
screen.blit(blob.image, spot)

挑战

困难

把史莱姆带进洞穴。

将 blob.png 和 blob_walk.png 加载到 blob_img 和 blob_walk_img 中，并添加 solid() 后面所示的 Blob 类。
在地图循环之前创建 blobs = pygame.sprite.Group()；每个 E 都会添加一个 Blob(rect.midbottom)。
在尖刺处理之后，按示例更新 blobs，并执行踩踏处理或设置 hurt。在尖刺之后绘制史莱姆。

按下“开始”：史莱姆会在地面上巡逻，踩踏会消灭一只。然后点击“检查”。

亲手试试

import pygame

TILE = 36
WIDTH, HEIGHT = 576, 360
SPEED = 4
GRAVITY = 1
JUMP = -15
MAX_FALL = 12

LEVEL = [
    "................................................................",
    "................................................................",
    "................................................................",
    "................................................................",
    "#..............................................................#",
    "#....................C.........................#####...........#",
    "#......CC...C................CC.....CC.........#####.....CC....#",
    "#....................#.........................D...............#",
    "#.P.........#...E....#...^.......K......E......D.C....^......F.#",
    "#######..####################..##########################..#####",
]

pygame.init()
screen = pygame.display.set_mode((WIDTH, HEIGHT))
pygame.display.set_caption("Moss Caves")
clock = pygame.time.Clock()
font = pygame.font.Font("assets/fonts/pixel.ttf", 24)


def load(name):
    return pygame.image.load("assets/images/" + name).convert_alpha()


background = pygame.image.load("assets/backgrounds/forest.png").convert_alpha()
grass_img = load("grass.png")
grass_left_img = load("grass_left.png")
grass_right_img = load("grass_right.png")
dirt_img = load("dirt.png")
player_img = load("player.png")
coin_img = load("coin.png")
spikes_img = load("spikes.png")
heart_img = load("heart.png")
heart_empty_img = load("heart_empty.png")


def solid(row, col):
    if row < 0 or row >= len(LEVEL) or col < 0 or col >= len(LEVEL[0]):
        return False
    return LEVEL[row][col] == "#"


walls = []
tiles = []
coins = []
spikes = []
for row, line in enumerate(LEVEL):
    for col, char in enumerate(line):
        rect = pygame.Rect(col * TILE, row * TILE, TILE, TILE)
        if char == "#":
            if solid(row - 1, col):
                image = dirt_img
            elif not solid(row, col - 1) and solid(row, col + 1):
                image = grass_left_img
            elif solid(row, col - 1) and not solid(row, col + 1):
                image = grass_right_img
            else:
                image = grass_img
            walls.append(rect)
            tiles.append((image, rect))
        elif char == "P":
            start = rect.midbottom
        elif char == "C":
            coins.append(rect)
        elif char == "^":
            spikes.append(pygame.Rect(rect.x, rect.y + 18, TILE, 18))

level_width = len(LEVEL[0]) * TILE
player = player_img.get_rect(midbottom=start)
vel_y = 0
on_ground = False
camera_x = 0
coins_collected = 0
lives = 3

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        elif event.type == pygame.KEYDOWN and event.key in (pygame.K_SPACE, pygame.K_UP):
            if on_ground:
                vel_y = JUMP
        elif event.type == pygame.KEYUP and event.key in (pygame.K_SPACE, pygame.K_UP):
            if vel_y < -4:
                vel_y = -4

    keys = pygame.key.get_pressed()
    dx = 0
    if keys[pygame.K_LEFT]:
        dx -= SPEED
    if keys[pygame.K_RIGHT]:
        dx += SPEED

    player.x += dx
    for wall in walls:
        if player.colliderect(wall):
            if dx > 0:
                player.right = wall.left
            elif dx < 0:
                player.left = wall.right

    vel_y = min(vel_y + GRAVITY, MAX_FALL)
    player.y += vel_y
    on_ground = False
    for wall in walls:
        if player.colliderect(wall):
            if vel_y > 0:
                player.bottom = wall.top
                on_ground = True
            elif vel_y < 0:
                player.top = wall.bottom
            vel_y = 0

    hurt = False
    if player.top > HEIGHT:
        hurt = True

    for coin in coins[:]:
        if player.colliderect(coin):
            coins.remove(coin)
            coins_collected += 1
    for spike in spikes:
        if player.colliderect(spike):
            hurt = True

    if hurt:
        lives -= 1
        player.midbottom = start
        vel_y = 0

    camera_x = player.centerx - WIDTH // 2
    camera_x = max(0, min(camera_x, level_width - WIDTH))

    shift = camera_x // 3 % 72
    for y in range(0, HEIGHT, 72):
        for x in range(-shift, WIDTH, 72):
            screen.blit(background, (x, y))
    for image, rect in tiles:
        screen.blit(image, (rect.x - camera_x, rect.y))
    for coin in coins:
        screen.blit(coin_img, (coin.x - camera_x, coin.y))
    for spike in spikes:
        screen.blit(spikes_img, (spike.x - camera_x, spike.y - 18))
    screen.blit(player_img, (player.x - camera_x, player.y))
    for i in range(3):
        if i < lives:
            screen.blit(heart_img, (10 + i * 40, 8))
        else:
            screen.blit(heart_empty_img, (10 + i * 40, 8))
    text = font.render(f"Coins: {coins_collected}", True, (255, 255, 255))
    screen.blit(text, text.get_rect(topright=(WIDTH - 12, 14)))
    pygame.display.flip()
    clock.tick(60)

pygame.quit()