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外星人入侵

1. 项目需求

在游戏《外星人入侵》中，玩家控制着一艘最初出现在屏幕底部中央的飞船。玩家可以使用箭头键左右移动飞船，还可使用空格键进行射击。游戏开始时，一群外星人出现在天空中，他们在屏幕中向下移动。玩家的任务是射杀这些外星人。

玩家将所有外星人都消灭干净后，将出现一群新的外星人，他们移动的速度更快。只要有外星人撞到了玩家的飞船或到达了屏幕底部，玩家就损失一艘飞船。玩家损失三艘飞船后，游戏结束。

我们将添加一个Play按钮，用于根据需要启动游戏以及在游戏结束后重启游戏。我们还将修改这个游戏，使其在玩家的等级提高时加快节奏，并实现一个记分系统。

2. 代码

　　aliens_invasion.py

import sys
import pygame   #包含开发游戏所需功能
from pygame.sprite import Group
from settings import Settings
from game_stats import GameStats
from scoreboard import Scoreboard
from button import Button
from ship import Ship
#from alien import Alien
import game_functions as gf
 
def run_game():
    #初始化游戏并创建一个屏幕对象
    pygame.init()       #初始化背景设置
    ai_settings = Settings()
    screen = pygame.display.set_mode(
        (ai_settings.screen_width, ai_settings.screen_height)) #创建名为screen的显示窗口
    pygame.display.set_caption("Alien Invasion")
 
    #创建Play按钮
    play_button = Button(ai_settings, screen, "Play")
 
    #创建一个用于存储游戏统计信息的实例,并创建记分牌
    stats = GameStats(ai_settings)
    sb = Scoreboard(ai_settings, screen, stats)
 
    #创建一艘飞船
    ship = Ship(ai_settings, screen) #必须在主while循环前面创建该实例，以免每次循环时都创建一艘飞船
    #创建一个用于存储子弹的编组
    bullets = Group()
    #创建一个外星人
    aliens = Group()
 
    #创建外星人群
    gf.create_fleet(ai_settings, screen, ship, aliens)
 
    #开始游戏的主循环
    while True:
        gf.check_events(ai_settings, screen, stats, sb, play_button, ship, aliens, bullets)
 
        if stats.game_active:
            ship.update()
            gf.update_bullets(ai_settings, screen, stats, sb, ship, aliens, bullets)
            gf.update_aliens(ai_settings, screen, stats, sb, ship, aliens, bullets)
 
        gf.update_screen(ai_settings, screen, stats, sb, ship, aliens, bullets, play_button)
 
run_game()

　　bullet.py

import pygame
from pygame.sprite import Sprite
 
class Bullet(Sprite):
    """一个对飞船发射的子弹进行管理的类"""
    def __init__(self, ai_settings, screen, ship):
        """在飞船所处的位置创建一个子弹对象"""
        super(Bullet, self).__init__()
        self.screen = screen
 
        #在（0，0）处创建一个表示子弹的矩形，再设置正确的位置
        self.rect = pygame.Rect(0, 0, ai_settings.bullet_width,
                                ai_settings.bullet_height)
        self.rect.centerx = ship.rect.centerx       #定义子弹初始x轴坐标
        self.rect.top = ship.rect.top               #定义子弹初始y轴坐标
 
        #存储用小数表示的子弹位置
        self.y = float(self.rect.y)
        self.color = ai_settings.bullet_color
        self.speed_factor = ai_settings.bullet_speed_factor
 
    def update(self):
        """向上移动子弹"""
        #更新表示子弹位置的小数值
        self.y -= self.speed_factor
        #更新表示子弹的rect的位置
        self.rect.y = self.y
 
    def draw_bullet(self):
        """在屏幕上绘制子弹"""
        pygame.draw.rect(self.screen, self.color, self.rect)

　　button.py

import pygame.font
 
class Button():
    def __init__(self, ai_setting, screen, msg):
        """初始化按钮的属性"""
        self.screen = screen
        self.screen_rect = screen.get_rect()
 
        #设置按钮的尺寸和其他属性
        self.width, self.height = 200, 50
        self.button_color = (0, 255, 0)
        self.text_color = (255, 255, 255)
        self.font = pygame.font.SysFont(None, 48)
 
        #创建按钮的rect对象，并使其居中
        self.rect = pygame.Rect(0, 0, self.width, self.height)
        self.rect.center = self.screen_rect.center
 
        #按钮的标签只需创建一次
        self.prep_msg(msg)
 
    def prep_msg(self, msg):
        """将msg渲染为图像，并使其在按钮上居中"""
        self.msg_image = self.font.render(msg, True, self.text_color,
                                          self.button_color)
        self.msg_image_rect = self.msg_image.get_rect()
        self.msg_image_rect.center = self.rect.center
 
    def draw_button(self):
        #绘制一个用颜色填充的按钮，再绘制文本
        self.screen.fill(self.button_color, self.rect)
        self.screen.blit(self.msg_image, self.msg_image_rect)

　　game_function.py

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import sys
import pygame
from bullet import Bullet
from alien import Alien
from time import sleep
 
def check_keydown_events(event, ai_settings, screen, ship, bullets):
    """响应按键"""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = True
    elif event.key == pygame.K_LEFT:
        ship.moving_left = True
    elif event.key == pygame.K_SPACE:
        fire_bullet(ai_settings, screen, ship, bullets)
    elif event.key == pygame.K_q:
        sys.exit()
 
def fire_bullet(ai_settings, screen, ship, bullets):
    """如果还没有到达限制，就发射一颗子弹"""
    #创建新子弹，并将其加入到编组bullets中
    if len(bullets) < ai_settings.bullets_allowed:
        new_bullet = Bullet(ai_settings, screen, ship)
        bullets.add(new_bullet)
 
def check_keyup_events(event, ship):
    """响应松开"""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = False
    elif event.key == pygame.K_LEFT:
        ship.moving_left = False
 
def check_events(ai_settings, screen, stats, sb, play_button, ship, aliens, bullets):
    """响应按键和鼠标事件"""
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()
 
        elif event.type == pygame.KEYDOWN:
            check_keydown_events(event,ai_settings, screen, ship, bullets)
        elif event.type == pygame.KEYUP:
            check_keyup_events(event, ship)
        elif event.type == pygame.MOUSEBUTTONDOWN:
            mouse_x, mouse_y = pygame.mouse.get_pos()
            check_play_button(ai_settings, screen, stats, sb, play_button,
                              ship, aliens, bullets, mouse_x, mouse_y)
 
def check_play_button(ai_settngs, screen, stats, sb, play_button, ship, aliens, bullets, mouse_x, mouse_y):
    """在玩家单击Play按钮时开始新游戏"""
    button_clicked = play_button.rect.collidepoint(mouse_x, mouse_y)
    if button_clicked and not stats.game_active:
        #重置游戏设置
        ai_settngs.initialize_dynamic_settings()
 
        #隐藏光标
        pygame.mouse.set_visible(False)
 
        #重置游戏统计信息
        stats.reset_stats()
        stats.game_active = True
 
        #重置记分牌图像
        sb.prep_score()
        sb.prep_high_score()
        sb.prep_level()
        sb.prep_ships()
 
        #清空外星人列表和子弹列表
        aliens.empty()
        bullets.empty()
 
        #创建一群新的外星人，并让飞船居中
        create_fleet(ai_settngs, screen, ship, aliens)
        ship.center_ship()
 
def update_screen(ai_settings, screen, stats, sb, ship, aliens, bullets, play_button):
    """更新屏幕上的图像，并切换到新屏幕"""
    #每次循环时都重绘屏幕
    screen.fill(ai_settings.bg_color)
    #在飞船和外星人后面重绘所有子弹
    for bullet in bullets.sprites():
        bullet.draw_bullet()
    ship.blitme()
    aliens.draw(screen)
 
    #显示得分
    sb.show_score()
 
    #如果游戏处于非活动状态，就绘制Play按钮
    if not stats.game_active:
        play_button.draw_button()
 
    #让最近绘制的屏幕可见
    pygame.display.flip()
 
def update_bullets(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """更新子弹的位置，并删除已消失的子弹"""
    #更新子弹的位置
    bullets.update()
 
    #删除已消失的子弹
    for bullet in bullets.copy():
        if bullet.rect.bottom <= 0:
            bullets.remove(bullet)
 
    check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship, aliens, bullets)
 
def check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """影响子弹和外星人的碰撞"""
    #删除发生碰撞的子弹和外星人
    collisions = pygame.sprite.groupcollide(bullets, aliens, True, True)
 
    if collisions:
        for aliens in collisions.values():
            stats.score += ai_settings.alien_points
            sb.prep_score()
        check_high_score(stats, sb)
 
    if len(aliens) == 0:
        #如果整群外星人都被消灭，就提高一个等级
        bullets.empty()
        ai_settings.increase_speed()
 
        #提高等级
        stats.level += 1
        sb.prep_level()
 
        create_fleet(ai_settings, screen, ship, aliens)
 
def get_number_aliens_x(ai_settings, alien_width):
    """计算每行可容纳多少外星人"""
    available_space_x = ai_settings.screen_width - 2 *alien_width
    number_aliens_x = int(available_space_x / (2 * alien_width))
    return number_aliens_x
 
def get_number_rows(ai_settings, ship_height, alien_height):
    """计算屏幕可容纳多少行外星人"""
    available_space_y = (ai_settings.screen_height - (3 * alien_height) -
                        ship_height)
    number_rows = int(available_space_y / (2* alien_height))
    return  number_rows
 
def create_alien(ai_settings, screen, aliens, alien_number, row_number):
    """创建一个外星人并将其放在当前行"""
    alien = Alien(ai_settings, screen)
    alien_width = alien.rect.width
    alien.x = alien_width + 2 * alien_width * alien_number
    alien.rect.x = alien.x
    alien.rect.y = alien.rect.height + 2 * alien.rect.height * row_number
    aliens.add(alien)
 
def  create_fleet(ai_settings, screen, ship, aliens):
    """创建外星人群"""
    #创建一个外星人，并计算可容纳多少个外星人
    alien = Alien(ai_settings, screen)
    number_aliens_x = get_number_aliens_x(ai_settings, alien.rect.width)
    number_rows = get_number_rows(ai_settings, ship.rect.height, alien.rect.height)
 
    #创建外星人群
    for row_number in range(number_rows):
        for alien_number in range(number_aliens_x):
            create_alien(ai_settings, screen, aliens, alien_number, row_number)
 
def ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """响应飞船被外星人撞到"""
    if stats.ship_left > 0:
        #将ship_left减1
        stats.ship_left -= 1
 
        #更新记分牌
        sb.prep_ships()
 
        #清空外星人列表和子弹列表
        aliens.empty()
        bullets.empty()
 
        #创建一群新的外星人，并将飞船放到屏幕底端中央
        create_fleet(ai_settings, screen, ship, aliens)
        ship.center_ship()
 
        #暂停
        sleep(0.5)
    else:
        stats.game_active = False
        pygame.mouse.set_visible(True)
 
def check_aliens_bottom(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """检查是否有外星人到达了屏幕底端"""
    screen_rect = screen.get_rect()
    for alien in aliens.sprites():
        if alien.rect.bottom >= screen_rect.bottom:
            #像飞船被撞到一样进行处理
            ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets)
            break
 
 
def update_aliens(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """检查是否有外星人到达屏幕边缘
    然后更新所有外星人的位置
    """
    check_fleet_edges(ai_settings, aliens)
    aliens.update()
 
    #检查外星人和飞船之间的碰撞
    if pygame.sprite.spritecollideany(ship, aliens):
        ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets)
 
 
    #检查是否有外星人到达屏幕底端
    check_aliens_bottom(ai_settings,screen, stats, sb, ship, aliens, bullets)
 
def check_fleet_edges(ai_settings, aliens):
    """有外星人到达边缘时采取相应的措施"""
    for alien in aliens.sprites():
        if alien.check_edges():
            change_fleet_direction(ai_settings, aliens)
            break
 
def change_fleet_direction(ai_settings, aliens):
    """将整群外星人下移，并改变它们的方向"""
    for alien in aliens.sprites():
        alien.rect.y += ai_settings.fleet_drop_speed
    ai_settings.fleet_direction *= -1
 
def check_high_score(stats, sb):
    """检查是否诞生了新的高分"""
    if stats.score > stats.high_score:
        stats.high_score = stats.score
        sb.prep_high_score()

　　game_stats.py

class GameStats():
    """跟踪游戏的统计信息"""
    def __init__(self, ai_settings):
        """初始化统计信息"""
        self.ai_settings = ai_settings
        self.reset_stats()
 
        #游戏刚启动时处于活动状态
        self.game_active = False
        #在任何情况下都不应重置最高得分
        self.high_score = 0
 
    def reset_stats(self):
        """初始化在游戏运行期间可能变化的统计信息"""
        self.ship_left = self.ai_settings.ship_limit
        self.score = 0
        self.level = 1

　　scoreboard.py

import pygame.font
from pygame.sprite import Group
 
from ship import Ship
 
class Scoreboard():
    """显示得分信息的类"""
 
    def __init__(self, ai_settings, screen, stats):
        """初始化显示得分涉及的属性"""
        self.screen = screen
        self.screen_rect = screen.get_rect()
        self.ai_settings = ai_settings
        self.stats = stats
 
        #显示得分信息时使用的字体设置
        self.text_color = (30, 30, 30)
        self.font = pygame.font.SysFont(None, 48)
 
        #准备包含最高得分和当前得分的图像
        self.prep_score()
        self.prep_high_score()
        self.prep_level()
        self.prep_ships()
 
    def prep_ships(self):
        """显示还余下多少艘飞船"""
        self.ships = Group()
        for ship_number in range(self.stats.ship_left):
            ship = Ship(self.ai_settings, self.screen)
            ship.rect.x = 10 + ship_number * ship.rect.width
            ship.rect.y = 10
            self.ships.add(ship)
 
 
    def prep_level(self):
        """将等级转换为渲染的图像"""
        self.level_image = self.font.render(str(self.stats.level), True,
                                            self.text_color, self.ai_settings.bg_color)
        #将等级放在得分下方
        self.level_rect = self.level_image.get_rect()
        self.level_rect.right = self.score_rect.right
        self.level_rect.top = self.score_rect.bottom + 10
 
 
    def prep_high_score(self):
        """将最高得分转换为渲染的图像"""
        high_score = int(round(self.stats.high_score, -1))
        high_score_str = "{:,}".format(high_score)
        self.high_score_image = self.font.render(high_score_str, True,
                                                 self.text_color, self.ai_settings.bg_color)
 
        #将最高得分放在屏幕顶部中央
        self.high_score_rect = self.high_score_image.get_rect()
        self.high_score_rect.centerx = self.screen_rect.centerx
        self.high_score_rect.top = self.screen_rect.top
 
 
    def prep_score(self):
        """将得分转换为一幅渲染的图像"""
        rounded_score = int(round(self.stats.score, -1))
        score_str = "{:,}".format(rounded_score)
        self.score_image = self.font.render(score_str, True, self.text_color,
                                            self.ai_settings.bg_color)
 
        #将得分放在屏幕右上角
        self.score_rect = self.score_image.get_rect()
        self.score_rect.right = self.screen_rect.right - 20
        self.score_rect.top = 20
 
    def show_score(self):
        """在屏幕上显示飞船和得分"""
        self.screen.blit(self.score_image, self.score_rect)
        self.screen.blit(self.high_score_image, self.high_score_rect)
        self.screen.blit(self.level_image, self.level_rect)
 
        #绘制飞船
        self.ships.draw(self.screen)

　　settings.py

class Settings():
    """存储《外星人入侵》的所有设置的类"""
    def __init__(self):
        """初始化游戏的静态设置"""
        #屏幕设置
        self.screen_width = 1200
        self.screen_height = 800
        self.bg_color = (0, 0, 0)
 
        #飞船的设置
        self.ship_speed_factor = 1.5
        self.ship_limit = 3
 
        #外星人设置
        self.fleet_drop_speed = 10
 
        #以什么样的速度加快游戏节奏
        self.speedup_scale = 1.1
        #外星人点数的提高速度
        self.score_scale = 1.5
 
        self.initialize_dynamic_settings()
 
        #子弹设置
        self.bullet_speed_factor = 2
        self.bullet_width = 3
        self.bullet_height = 15
        self.bullet_color = (255, 255, 255)
        self.bullets_allowed = 3
 
 
    def initialize_dynamic_settings(self):
        """初始化随游戏进行而变化的设置"""
        self.ship_speed_factor = 1.5
        self.bullet_speed_factor = 3
        self.alien_speed_factor = 1
 
        #fleet_direction为1表示向右；为-1表示向左
        self.fleet_direction = 1
 
        #记分
        self.alien_points = 50
 
    def increase_speed(self):
        """提高速度设置和外星人点数"""
        self.ship_speed_factor *= self.speedup_scale
        self.bullet_speed_factor *= self.speedup_scale
        self.alien_speed_factor *= self.speedup_scale
 
        self.alien_points = int(self.alien_points * self.score_scale)
        #print(self.alien_points)

　　ship.py

import pygame
from pygame.sprite import Sprite
class Ship(Sprite):     #Ship继承Sprite
    def __init__(self, ai_settings, screen):
        """初始化飞船，并设置其起始位置"""
        super(Ship, self).__init__()
        self.screen = screen
        self.ai_settings = ai_settings
 
        #加载飞船图像并获取其外接矩形
        self.image = pygame.image.load('image/ship.bmp')
        self.rect = self.image.get_rect()
        self.screen_rect = screen.get_rect()
 
        #将每艘新飞船放在屏幕底部中央
        self.rect.centerx = self.screen_rect.centerx
        self.rect.bottom = self.screen_rect.bottom
 
        #在飞船的属性center中存储小数值
        self.center = float(self.rect.centerx)
 
        #移动标志
        self.moving_right = False
        self.moving_left = False
 
    def update(self):
        """根据移动标志调整飞船的位置"""
        #更新飞船的center值，而不是rect
        if self.moving_right and (self.rect.right < self.screen_rect.right):
            self.center += self.ai_settings.ship_speed_factor
        if self.moving_left and (self.rect.left > 0):        #如果使用elif代码块来处理向左移动，右箭头键始终处于优先地位
            self.center -= self.ai_settings.ship_speed_factor
 
        #根据self.center更新rect对象
        self.rect.centerx = self.center
 
 
 
    def blitme(self):
        """在指定位置绘制飞船"""
        self.screen.blit(self.image, self.rect)
 
    def center_ship(self):
        """让飞船在屏幕上居中"""
        self.center = self.screen_rect.centerx