用爱心表示生命

本课属于 Coddy Pygame 学习旅程的“游戏规则”单元。第 8 课，共 30 课。

现在游戏有 3 条生命，底部会显示 Lives: 3。玩家看一排爱心，比看数字更快。素材包中有 heart.png 和 heart_empty.png，两张图片的尺寸都是 36 × 36。

在 set_mode 之后加载每张图片一次：

heart = pygame.image.load("assets/images/heart.png").convert_alpha()
heart_empty = pygame.image.load("assets/images/heart_empty.png").convert_alpha()

然后用 for 循环绘制 3 个位置。当 i 小于剩余生命数时，位置 i 显示为满心：

for i in range(3):
    if i < lives:
        screen.blit(heart, (10 + i * 40, 10))
    else:
        screen.blit(heart_empty, (10 + i * 40, 10))

剩余 2 条生命时，位置 0 和 1 显示为满心，位置 2 显示为空心。空心爱心让这一排保持相同的长度，这样玩家就能看到游戏开始时有多少条生命，而不只是剩余多少条。

挑战

中等

用爱心显示剩余生命，而不是用文字。

在 set_mode 之后加载一次 assets/images/heart.png 和 assets/images/heart_empty.png。
在 draw_game() 中，在 x 坐标 10、50 和 90，y 坐标 10 处绘制三个爱心：每剩余一条生命，就显示一个完整的爱心；每失去一条生命，就显示一个空心爱心。
移除 Lives: 文本。

按“开始”，然后受到一次攻击：最后一个爱心会变为空心。接着按“检查”。

亲手试试

import random
import pygame

pygame.init()
screen = pygame.display.set_mode((480, 360))
pygame.display.set_caption("Meteor Dodge")
clock = pygame.time.Clock()
font = pygame.font.Font("assets/fonts/pixel.ttf", 24)
big_font = pygame.font.Font("assets/fonts/pixel.ttf", 48)
WHITE = (240, 240, 240)
PLATE = (60, 60, 90)


def reset():
    global player, rock, score, lives
    player = pygame.Rect(220, 300, 40, 40)
    rock = pygame.Rect(random.randint(0, 456), -24, 24, 24)
    score = 0
    lives = 3


def draw_menu():
    screen.fill((30, 30, 46))
    title = big_font.render("Meteor Dodge", True, WHITE)
    title_rect = title.get_rect(center=(240, 140))
    pygame.draw.rect(screen, PLATE, title_rect.inflate(24, 12))
    screen.blit(title, title_rect)
    hint = font.render("Press Enter to play", True, WHITE)
    screen.blit(hint, hint.get_rect(center=(240, 200)))


def draw_game():
    screen.fill((30, 30, 46))
    pygame.draw.rect(screen, (255, 196, 0), player)
    pygame.draw.rect(screen, (235, 80, 80), rock)
    score_text = font.render(f"Score: {score}", True, WHITE)
    score_rect = score_text.get_rect(topright=(470, 10))
    pygame.draw.rect(screen, PLATE, score_rect.inflate(12, 8))
    screen.blit(score_text, score_rect)
    lives_text = font.render(f"Lives: {lives}", True, WHITE)
    screen.blit(lives_text, (10, 330))


def play_frame():
    global score, lives, state
    keys = pygame.key.get_pressed()
    if keys[pygame.K_LEFT]:
        player.x -= 6
    if keys[pygame.K_RIGHT]:
        player.x += 6
    player.clamp_ip(screen.get_rect())

    rock.y += 4
    if rock.top > 360:
        rock.y = -24
        rock.x = random.randint(0, 456)
        score += 1
    if rock.colliderect(player):
        rock.y = -24
        rock.x = random.randint(0, 456)
        lives -= 1
        if lives == 0:
            state = "over"
    draw_game()


def draw_over():
    draw_game()
    message = big_font.render("Game over", True, WHITE)
    screen.blit(message, message.get_rect(center=(240, 160)))
    hint = font.render("Press R to play again", True, WHITE)
    screen.blit(hint, hint.get_rect(center=(240, 200)))


reset()
state = "menu"

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_RETURN and state == "menu":
                state = "play"
            elif event.key == pygame.K_r and state == "over":
                reset()
                state = "play"

    if state == "menu":
        draw_menu()
    elif state == "play":
        play_frame()
    else:
        draw_over()
    pygame.display.flip()
    clock.tick(60)

pygame.quit()

游戏规则中的所有课

自己练习： Pygame 在线编辑器