掉出关卡

本课属于 Coddy Pygame 学习旅程的“游戏世界”单元。第 18 课，共 36 课。

地面上有一个坑。走进去后，玩家会一直往下掉，直到消失在视野中。它的 y 坐标会不断增大，没有任何东西能让它回来。

关卡在窗口底部结束，y = 360。一旦玩家的顶部低于这个位置，整个身体就离开了关卡：把它放回起点并停止下落。

if player.top > 360:
    player.midbottom = start
    vel_y = 0

start 是地图循环为 P 瓷砖保存的位置：该瓷砖底部的中点，也就是玩家最初站立的地方。之后，玩家会在这里失去一条命。

挑战

简单

玩家掉出关卡后，让其回到关卡中。

在垂直碰撞处理之后，当 player.top > 360 时，设置 player.midbottom = start。
同时在那里设置 vel_y = 0。

按“开始”，然后走进坑里：玩家会回到起点。接着按“检查”。

亲手试试

import pygame

TILE = 36
SPEED = 4
GRAVITY = 1
JUMP = -15
MAX_FALL = 12

LEVEL = [
    "................",
    "................",
    "................",
    "................",
    "................",
    "................",
    "..........###...",
    "................",
    "#.P.............",
    "#######....#####",
]

pygame.init()
screen = pygame.display.set_mode((576, 360))
pygame.display.set_caption("Pits")
clock = pygame.time.Clock()

background = pygame.image.load("assets/backgrounds/clouds.png").convert_alpha()
block_img = pygame.image.load("assets/images/block.png").convert_alpha()
player_img = pygame.image.load("assets/images/player.png").convert_alpha()

walls = []
for row, line in enumerate(LEVEL):
    for col, char in enumerate(line):
        if char == "#":
            walls.append(pygame.Rect(col * TILE, row * TILE, TILE, TILE))
        elif char == "P":
            start = (col * TILE + TILE // 2, row * TILE + TILE)

player = player_img.get_rect(midbottom=start)
vel_y = 0
on_ground = False

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

    for y in range(0, 360, 72):
        for x in range(0, 576, 72):
            screen.blit(background, (x, y))
    for wall in walls:
        screen.blit(block_img, wall)
    screen.blit(player_img, player)
    pygame.display.flip()
    clock.tick(60)

pygame.quit()

游戏世界中的所有课

自己练习： Pygame 在线编辑器