Space game Lesson 12: shield

Space game number 12 course ： shield

This is us. “Shmup” Project No 9 part . If you haven't read through the previous section , Please from The first 1 part Start . In this lesson , We will add a shield for players and a bar for displaying shield level .

video

You can watch the video of this course here ：

Add shield

Now? , Our player was hit and destroyed by a meteor . It's not very interesting , So we want to add one to the player shield attribute , It is 0 - 100 The number of .

class Player(pygame.sprite.Sprite):
    def __init__(self):
        self.speedx = 0
        self.shield = 100

Now? , Whenever a player is hit by a meteor , We can subtract a little from the shield . When the shield reaches 0 when , Players are destroyed . To make things more interesting , We can use meteors radius Attribute makes large meteors cause more damage than small meteors .

In the next video , We will add some shields for players , So we won't die so easily .

Hurt players

at present , Our enemy and player collision code is very simple ：

    # check to see if a mob hit the player
    hits = pygame.sprite.spritecollide(player, mobs, False, pygame.sprite.collide_circle)
    if hits:
        running = False

We need to make some changes ：

    # check to see if a mob hit the player
    hits = pygame.sprite.spritecollide(player, mobs, True, pygame.sprite.collide_circle)
    for hit in hits:
        player.shield -= hit.radius * 2
        if player.shield <= 0:
            running = False

We will spritecollide The parameters of the function False Change to True, Because we want the meteor to be deleted when it hits . If we don't , Then meteors will continue to exist , When it moves , There will be another collision in the next frame , And so on . Besides , We may hit multiple meteors at the same time ,hits There can be multiple projects . We go through a cycle hits, And deduct some shields for each hit according to its radius . Last , If the player's shield reaches 0, The game will be over .

One thing you may have noticed is , Because we are removing any enemies that hit the player , therefore , We are reducing the total number of enemies in the game . We hope it stays the same , So whenever we remove an enemy , We all need to create a new enemy . This is how we generate primitive enemies , As shown below ：

for i in range(8):
    m = Mob()
    all_sprites.add(m)
    mobs.add(m)

but , We need to create a new enemy , This is duplicate code , It's a bad thing . contrary , We will mob Create code to move into a function , We can use it when we need it ：

def newmob():
    m = Mob()
    all_sprites.add(m)
    mobs.add(m)

Now? , We can start the game , When we hit the enemy , And when we need to replace the enemy that hit the player , You can use this function ：

for i in range(8):
    newmob()

# check to see if a bullet hit a mob
hits = pygame.sprite.groupcollide(mobs, bullets, True, True)
for hit in hits:
    score += 50 - hit.radius
    random.choice(expl_sounds).play()
    newmob()

# check to see if a mob hit the player
hits = pygame.sprite.spritecollide(player, mobs, True, pygame.sprite.collide_circle)
for hit in hits:
    player.shield -= hit.radius * 2
    newmob()
    if player.shield <= 0:
        running = False

Shield ruler

We have a shield value , It's working , But unless the player can see this value , Otherwise it is not very useful . We need to create a display , But it's not just about displaying numbers , We will make a bar chart , Show the full of shields / empty ：

def draw_shield_bar(surf, x, y, pct):
    if pct < 0:
        pct = 0
    BAR_LENGTH = 100
    BAR_HEIGHT = 10
    fill = (pct / 100) * BAR_LENGTH
    outline_rect = pygame.Rect(x, y, BAR_LENGTH, BAR_HEIGHT)
    fill_rect = pygame.Rect(x, y, fill, BAR_HEIGHT)
    pygame.draw.rect(surf, GREEN, fill_rect)
    pygame.draw.rect(surf, WHITE, outline_rect, 2)

This function works in the same way as we previously defined draw_text Function similar to . It will draw a length of BAR_LENGTH、 High for BAR_HEIGHT Bar of , be located (x, y) The column and press pct Value padding . We will draw two rectangles ： The first rectangle will be a white outline , The second rectangle is filled with green . We add a call to this function in the drawing part of the game loop ：

draw_text(screen, str(score), 18, WIDTH / 2, 10)
draw_shield_bar(screen, 5, 5, player.shield)

Now we can see how many shields we have left when it descends ：

The complete code of this part

# KidsCanCode - Game Development with Pygame video series
# Shmup game - part 9
# Video link: https://www.youtube.com/watch?v=vvgWfNLgK9c
# Player shield
# Frozen Jam by tgfcoder <https://twitter.com/tgfcoder> licensed under CC-BY-3
# Art from Kenney.nl
import pygame
import random
from os import path

img_dir = path.join(path.dirname(__file__), 'img')
snd_dir = path.join(path.dirname(__file__), 'snd')

WIDTH = 480
HEIGHT = 600
FPS = 60

# define colors
WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
RED = (255, 0, 0)
GREEN = (0, 255, 0)
BLUE = (0, 0, 255)
YELLOW = (255, 255, 0)

# initialize pygame and create window
pygame.init()
pygame.mixer.init()
screen = pygame.display.set_mode((WIDTH, HEIGHT))
pygame.display.set_caption("Shmup!")
clock = pygame.time.Clock()

font_name = pygame.font.match_font('arial')
def draw_text(surf, text, size, x, y):
    font = pygame.font.Font(font_name, size)
    text_surface = font.render(text, True, WHITE)
    text_rect = text_surface.get_rect()
    text_rect.midtop = (x, y)
    surf.blit(text_surface, text_rect)

def newmob():
    m = Mob()
    all_sprites.add(m)
    mobs.add(m)

def draw_shield_bar(surf, x, y, pct):
    if pct < 0:
        pct = 0
    BAR_LENGTH = 100
    BAR_HEIGHT = 10
    fill = (pct / 100) * BAR_LENGTH
    outline_rect = pygame.Rect(x, y, BAR_LENGTH, BAR_HEIGHT)
    fill_rect = pygame.Rect(x, y, fill, BAR_HEIGHT)
    pygame.draw.rect(surf, GREEN, fill_rect)
    pygame.draw.rect(surf, WHITE, outline_rect, 2)

class Player(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.transform.scale(player_img, (50, 38))
        self.image.set_colorkey(BLACK)
        self.rect = self.image.get_rect()
        self.radius = 20
        # pygame.draw.circle(self.image, RED, self.rect.center, self.radius)
        self.rect.centerx = WIDTH / 2
        self.rect.bottom = HEIGHT - 10
        self.speedx = 0
        self.shield = 100

    def update(self):
        self.speedx = 0
        keystate = pygame.key.get_pressed()
        if keystate[pygame.K_LEFT]:
            self.speedx = -8
        if keystate[pygame.K_RIGHT]:
            self.speedx = 8
        self.rect.x += self.speedx
        if self.rect.right > WIDTH:
            self.rect.right = WIDTH
        if self.rect.left < 0:
            self.rect.left = 0

    def shoot(self):
        bullet = Bullet(self.rect.centerx, self.rect.top)
        all_sprites.add(bullet)
        bullets.add(bullet)
        shoot_sound.play()

class Mob(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image_orig = random.choice(meteor_images)
        self.image_orig.set_colorkey(BLACK)
        self.image = self.image_orig.copy()
        self.rect = self.image.get_rect()
        self.radius = int(self.rect.width * .85 / 2)
        # pygame.draw.circle(self.image, RED, self.rect.center, self.radius)
        self.rect.x = random.randrange(WIDTH - self.rect.width)
        self.rect.bottom = random.randrange(-80, -20)
        self.speedy = random.randrange(1, 8)
        self.speedx = random.randrange(-3, 3)
        self.rot = 0
        self.rot_speed = random.randrange(-8, 8)
        self.last_update = pygame.time.get_ticks()

    def rotate(self):
        now = pygame.time.get_ticks()
        if now - self.last_update > 50:
            self.last_update = now
            self.rot = (self.rot + self.rot_speed) % 360
            new_image = pygame.transform.rotate(self.image_orig, self.rot)
            old_center = self.rect.center
            self.image = new_image
            self.rect = self.image.get_rect()
            self.rect.center = old_center

    def update(self):
        self.rotate()
        self.rect.x += self.speedx
        self.rect.y += self.speedy
        if self.rect.top > HEIGHT + 10 or self.rect.left < -100 or self.rect.right > WIDTH + 100:
            self.rect.x = random.randrange(WIDTH - self.rect.width)
            self.rect.y = random.randrange(-100, -40)
            self.speedy = random.randrange(1, 8)

class Bullet(pygame.sprite.Sprite):
    def __init__(self, x, y):
        pygame.sprite.Sprite.__init__(self)
        self.image = bullet_img
        self.image.set_colorkey(BLACK)
        self.rect = self.image.get_rect()
        self.rect.bottom = y
        self.rect.centerx = x
        self.speedy = -10

    def update(self):
        self.rect.y += self.speedy
        # kill if it moves off the top of the screen
        if self.rect.bottom < 0:
            self.kill()

# Load all game graphics
background = pygame.image.load(path.join(img_dir, "starfield.png")).convert()
background_rect = background.get_rect()
player_img = pygame.image.load(path.join(img_dir, "playerShip1_orange.png")).convert()
bullet_img = pygame.image.load(path.join(img_dir, "laserRed16.png")).convert()
meteor_images = []
meteor_list = ['meteorBrown_big1.png', 'meteorBrown_med1.png', 'meteorBrown_med1.png',
               'meteorBrown_med3.png', 'meteorBrown_small1.png', 'meteorBrown_small2.png',
               'meteorBrown_tiny1.png']
for img in meteor_list:
    meteor_images.append(pygame.image.load(path.join(img_dir, img)).convert())
# Load all game sounds
shoot_sound = pygame.mixer.Sound(path.join(snd_dir, 'pew.wav'))
expl_sounds = []
for snd in ['expl3.wav', 'expl6.wav']:
    expl_sounds.append(pygame.mixer.Sound(path.join(snd_dir, snd)))
pygame.mixer.music.load(path.join(snd_dir, 'tgfcoder-FrozenJam-SeamlessLoop.ogg'))
pygame.mixer.music.set_volume(0.4)

all_sprites = pygame.sprite.Group()
mobs = pygame.sprite.Group()
bullets = pygame.sprite.Group()
player = Player()
all_sprites.add(player)
for i in range(8):
    newmob()

score = 0
pygame.mixer.music.play(loops=-1)
# Game loop
running = True
while running:
    # keep loop running at the right speed
    clock.tick(FPS)
    # Process input (events)
    for event in pygame.event.get():
        # check for closing window
        if event.type == pygame.QUIT:
            running = False
        elif event.type == pygame.KEYDOWN:
            if event.key == pygame.K_SPACE:
                player.shoot()

    # Update
    all_sprites.update()

    # check to see if a bullet hit a mob
    hits = pygame.sprite.groupcollide(mobs, bullets, True, True)
    for hit in hits:
        score += 50 - hit.radius
        random.choice(expl_sounds).play()
        newmob()

    # check to see if a mob hit the player
    hits = pygame.sprite.spritecollide(player, mobs, True, pygame.sprite.collide_circle)
    for hit in hits:
        player.shield -= hit.radius * 2
        newmob()
        if player.shield <= 0:
            running = False

    # Draw / render
    screen.fill(BLACK)
    screen.blit(background, background_rect)
    all_sprites.draw(screen)
    draw_text(screen, str(score), 18, WIDTH / 2, 10)
    draw_shield_bar(screen, 5, 5, player.shield)
    # *after* drawing everything, flip the display
    pygame.display.flip()

pygame.quit()

The first 10 part ： The explosion