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闪烁并递增计数

本课属于 Coddy Pygame 学习旅程的“音效与游戏体验”单元。第 23 课，共 23 课。

最后再做两处润色。玩家失去一条生命时，整个屏幕会短暂闪红，让人一眼就能注意到。得分时，数字会逐渐增加，而不是突然跳变。

红色闪光是一张与窗口同样大小的 Surface，填充为红色，并通过 set_alpha() 设置为半透明，透明度从 0（不可见）到 255（不透明）。在循环之前创建一次：

red = pygame.Surface((640, 480))
red.fill((255, 0, 0))
red.set_alpha(90)

失去生命时，将 flash = 12。每一帧都会让它递减，只要它大于 0，游戏就会在绘制文字之前，将 red 绘制到游戏世界上方。

对于得分，保留第二个数字 shown_score，并让它每一帧逐渐接近实际得分：

shown_score += (score - shown_score) * 0.2

绘制 round(shown_score)。游戏仍然用 score 来决定一切，只有显示效果会逐渐变化。这就是本章所有润色效果的原则：改变玩家看到和听到的内容，但绝不改变规则。

challenge icon

挑战

中等

被击中时闪红光；让分数逐渐增加。

  1. 创建 flash = 0、shown_score = 0 和 Surface red（alpha 90）。失去一条生命时，将 flash 设为 flash = 12。
  2. 在 explosions.update() 旁边，当 flash 大于 0 时将其减小，并让 shown_score 以 0.2 的幅度逐渐接近 score。
  3. 绘制完 world 后，当 flash 大于 0 时，在 (0, 0) 处绘制 red；显示 Score: {round(shown_score)}。

按下“开始”并被击中，画面会闪红光。然后点击“检查”。

亲手试试

import random
import pygame

pygame.init()
screen = pygame.display.set_mode((640, 480))
pygame.display.set_caption("Star Patrol")
clock = pygame.time.Clock()
font = pygame.font.Font(None, 32)

ship_image = pygame.image.load("assets/images/ship.png").convert_alpha()
laser_image = pygame.image.load("assets/images/laser.png").convert_alpha()
red_image = pygame.image.load("assets/images/enemy_red.png").convert_alpha()
green_image = pygame.image.load("assets/images/enemy_green.png").convert_alpha()
yellow_image = pygame.image.load("assets/images/enemy_yellow.png").convert_alpha()
explosion_frames = []
for number in range(1, 5):
    explosion_frames.append(pygame.image.load(f"assets/images/explosion_{number}.png").convert_alpha())

laser_sound = pygame.mixer.Sound("assets/sounds/laser.ogg")
laser_sound.set_volume(0.4)
explosion_sound = pygame.mixer.Sound("assets/sounds/explosion.ogg")
hit_sound = pygame.mixer.Sound("assets/sounds/hit.ogg")

WAVES = [(red_image, 6, 2), (green_image, 8, 2), (yellow_image, 10, 3)]


class Player(pygame.sprite.Sprite):
    def __init__(self):
        super().__init__()
        self.image = ship_image
        self.rect = self.image.get_rect(midbottom=(320, 470))
        self.mask = pygame.mask.from_surface(self.image)

    def update(self):
        keys = pygame.key.get_pressed()
        if keys[pygame.K_LEFT]:
            self.rect.x -= 6
        if keys[pygame.K_RIGHT]:
            self.rect.x += 6
        self.rect.clamp_ip(screen.get_rect())


class Laser(pygame.sprite.Sprite):
    def __init__(self, x, y):
        super().__init__()
        self.image = laser_image
        self.rect = self.image.get_rect(midbottom=(x, y))
        self.mask = pygame.mask.from_surface(self.image)

    def update(self):
        self.rect.y -= 10
        if self.rect.bottom < 0:
            self.kill()


class Enemy(pygame.sprite.Sprite):
    def __init__(self, image, x, y, speed):
        super().__init__()
        self.image = image
        self.rect = self.image.get_rect(center=(x, y))
        self.mask = pygame.mask.from_surface(self.image)
        self.speed = speed

    def update(self):
        self.rect.y += self.speed


class Explosion(pygame.sprite.Sprite):
    def __init__(self, center):
        super().__init__()
        self.index = 0
        self.timer = 0
        self.image = explosion_frames[0]
        self.rect = self.image.get_rect(center=center)

    def update(self):
        self.timer += 1
        if self.timer == 5:
            self.timer = 0
            self.index += 1
            if self.index == len(explosion_frames):
                self.kill()
            else:
                self.image = explosion_frames[self.index]


def play_music(path, loops=-1):
    pygame.mixer.music.load(path)
    pygame.mixer.music.play(loops)


def burst(center):
    for i in range(16):
        particles.append({
            "x": center[0],
            "y": center[1],
            "vx": random.uniform(-4, 4),
            "vy": random.uniform(-4, 4),
            "life": random.randint(15, 30),
        })


def spawn_wave(image, count, speed):
    for i in range(count):
        x = random.randint(40, 600)
        enemies.add(Enemy(image, x, -40 - i * 120, speed))


player = Player()
lasers = pygame.sprite.Group()
enemies = pygame.sprite.Group()
explosions = pygame.sprite.Group()
world = pygame.Surface((640, 480))
particles = []
shake = 0
last_shot = 0
score = 0
lives = 3
wave = 0
image, count, speed = WAVES[wave]
spawn_wave(image, count, speed)
pygame.mixer.music.set_volume(0.5)
play_music("assets/music/level.ogg")

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    if lives > 0 and wave < len(WAVES):
        player.update()
        keys = pygame.key.get_pressed()
        now = pygame.time.get_ticks()
        if keys[pygame.K_SPACE] and now - last_shot >= 250:
            lasers.add(Laser(player.rect.centerx, player.rect.top))
            last_shot = now
            laser_sound.play()
        lasers.update()
        enemies.update()
        for enemy in enemies:
            if enemy.rect.top > 480:
                enemy.kill()
                lives -= 1
                hit_sound.play()
        hits = pygame.sprite.groupcollide(enemies, lasers, True, True, pygame.sprite.collide_mask)
        for enemy in hits:
            score += 10
            explosion_sound.play()
            burst(enemy.rect.center)
            shake = min(shake + 6, 15)
            explosions.add(Explosion(enemy.rect.center))
        crashes = pygame.sprite.spritecollide(player, enemies, True, pygame.sprite.collide_mask)
        for enemy in crashes:
            lives -= 1
            hit_sound.play()
            explosions.add(Explosion(enemy.rect.center))
            burst(enemy.rect.center)
            shake = 15
        if not enemies:
            wave += 1
            if wave < len(WAVES):
                image, count, speed = WAVES[wave]
                spawn_wave(image, count, speed)
            else:
                play_music("assets/music/win.ogg", 0)
        if lives <= 0:
            play_music("assets/music/lose.ogg", 0)
    explosions.update()
    for p in particles:
        p["x"] += p["vx"]
        p["y"] += p["vy"]
        p["life"] -= 1
    particles = [p for p in particles if p["life"] > 0]

    world.fill((12, 14, 30))
    enemies.draw(world)
    lasers.draw(world)
    world.blit(player.image, player.rect)
    explosions.draw(world)
    for p in particles:
        pygame.draw.circle(world, (255, 170, 60), (p["x"], p["y"]), p["life"] // 10 + 1)

    offset = (0, 0)
    if shake > 0:
        amount = shake // 3
        offset = (random.randint(-amount, amount), random.randint(-amount, amount))
        shake -= 1
    screen.fill((0, 0, 0))
    screen.blit(world, offset)
    score_text = font.render(f"Score: {score}", True, (240, 240, 240))
    screen.blit(score_text, (10, 10))
    lives_text = font.render(f"Lives: {max(lives, 0)}", True, (240, 240, 240))
    screen.blit(lives_text, lives_text.get_rect(topright=(630, 10)))
    if wave < len(WAVES):
        wave_text = font.render(f"Wave {wave + 1}", True, (240, 240, 240))
        screen.blit(wave_text, wave_text.get_rect(midtop=(320, 10)))
    if lives <= 0:
        message = font.render("Game over", True, (240, 240, 240))
        screen.blit(message, message.get_rect(center=(320, 240)))
    elif wave == len(WAVES):
        message = font.render("You win!", True, (240, 240, 240))
        screen.blit(message, message.get_rect(center=(320, 240)))
    pygame.display.flip()
    clock.tick(60)

pygame.quit()
quiz icon自我测试

这节课包含一个小测验。开始学习即可作答，并记录你的进度。

音效与游戏体验中的所有课

1音效

加载音效事件触发音效音量音效与按住的按键

4屏幕震动与受击闪光

屏幕震动受击闪光受击停顿效果要适度

2音乐

背景音乐为每种状态播放音乐暂停音乐

5平滑运动

朝目标移动平滑的摄像机拾取时弹出任何帧率下都平滑

3粒子

一个粒子粒子爆发淡出并缩小移除失效粒子

6完善星际巡逻

星际巡逻音效每次命中都迸出火花项目课撞击时震动项目课闪烁并递增计数项目课

自己练习： Pygame 在线编辑器