Space shooting part 2-2: enemy spirit

Space shooting Part 2-2： enemy sprite

This is us. “Shmup” Project No 2 part ！ In this lesson , We will add some enemy elves for players to avoid . In this series of courses , We will use Python and Pygame Build a complete game . It applies to already known Python Basic knowledge and hope to deepen the understanding of Python Beginners who understand and learn the basic knowledge of programming games .

enemy sprite

At this point , We don't need to worry about our enemy elves What is it? , We just want them to appear on the screen . You may think your game is about spaceships avoiding meteors or unicorns avoiding flying pizza - In terms of code , It doesn't matter .

Remember that , We will name the enemy's Genie as a common name in the code . The fact proved that , For general objects that move in the game , There is a perfect word ：Mob.

We'll start by defining sprite attributes ：

class Mob(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface((30, 40))
        self.image.fill(RED)
        self.rect = self.image.get_rect()
        self.rect.x = random.randrange(WIDTH - self.rect.width)
        self.rect.y = random.randrange(-100, -40)
        self.speedy = random.randrange(1, 8)

The key here is to choose a suitable Mob Where it appears . We don't want them to just pop up , So we choose one at the top y value （y<0）, And one between the two sides x The random value .

Now? , about update(), We can move the genie quickly , But when the spirit disappears from the bottom ？ We can delete this wizard , Then generate another wizard , Or you can get exactly the same effect by moving the sprite back to a random position above the top ：

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

Generate enemies

We will hope to have many enemies , So we will build a new mobs Group to control all enemies . This will also make our programming easier in the next steps . then , We generate some Mob And add it to the Group ：

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

Now you should have an endless stream Mob Get off the screen , Just like this. ：

This is good , But let Mob It's a little boring to move directly down . Let us in x Add a little movement in the direction ：

class Mob(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface((30, 40))
        self.image.fill(RED)
        self.rect = self.image.get_rect()
        self.rect.x = random.randrange(WIDTH - self.rect.width)
        self.rect.y = random.randrange(-100, -40)
        self.speedy = random.randrange(1, 8)
        self.speedx = random.randrange(-3, 3)

    def update(self):
        self.rect.x += self.speedx
        self.rect.y += self.speedy
        if self.rect.top > HEIGHT + 10 or self.rect.left < -25 or self.rect.right > WIDTH + 20:
            self.rect.x = random.randrange(WIDTH - self.rect.width)
            self.rect.y = random.randrange(-100, -40)
            self.speedy = random.randrange(1, 8)

Please note that , We need to change if Statement so that in Mob Regenerate when leaving the screen Mob. Moving diagonally Mob Left the side before leaving the bottom , So we need to be Mob Reset it quickly when you leave the screen .

Your game should now look like this ：

In the next lesson , We will learn how to detect when two elves collide with each other （ Collision ）, And enable players to Mob Shoot .

The complete code of this part

# KidsCanCode - Game Development with Pygame video series
# Shmup game - part 2
# Video link: https://www.youtube.com/watch?v=-5GNbL33hz0
# Enemy sprites
import pygame
import random

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()

class Player(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface((50, 40))
        self.image.fill(GREEN)
        self.rect = self.image.get_rect()
        self.rect.centerx = WIDTH / 2
        self.rect.bottom = HEIGHT - 10
        self.speedx = 0

    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

class Mob(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface((30, 40))
        self.image.fill(RED)
        self.rect = self.image.get_rect()
        self.rect.x = random.randrange(WIDTH - self.rect.width)
        self.rect.y = random.randrange(-100, -40)
        self.speedy = random.randrange(1, 8)
        self.speedx = random.randrange(-3, 3)

    def update(self):
        self.rect.x += self.speedx
        self.rect.y += self.speedy
        if self.rect.top > HEIGHT + 10 or self.rect.left < -25 or self.rect.right > WIDTH + 20:
            self.rect.x = random.randrange(WIDTH - self.rect.width)
            self.rect.y = random.randrange(-100, -40)
            self.speedy = random.randrange(1, 8)

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

# 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

    # Update
    all_sprites.update()

    # Draw / render
    screen.fill(BLACK)
    all_sprites.draw(screen)
    # *after* drawing everything, flip the display
    pygame.display.flip()

pygame.quit()

The first 3 part ： Collision （ And bullets ）