Space shooting part 1: player spirit and control

Space shooting Part 1： Player sprites and controls

Let's make our first game ！ 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 .

Start

If you're not ready , Please return and complete the related Pygame introduction The first lesson of . We will use the [pygame template.py](https://github.com/kidscancode/gamedev/blob/master/tutorials/pygame template.py) The program is the starting point of this course .

In this series , We're going to make a “Shmup” or “Shoot 'em up” Style games . In our case , We will be pilots of a small spacecraft , Try to survive when meteors and other objects fly towards us .

First , Save with a new name pygame template.py file . such , When you need other new games , You can still have templates . I choose to save as ：shmup.py.

First , Let's change the game setting to the value of the game we are making ：

WIDTH = 480
HEIGHT = 600
FPS = 60

This will be a “ Vertical mode ” game , This means that the height of the window is greater than the width . This is also an action game , So we want to make sure our FPS High enough , So that the fast-moving Genie looks like it can move smoothly .60 It's pretty good .

Player spirit

The first component we want to add is a wizard representing players . Final , This will be a spaceship , But when you first started , Ignore the graphics a little , It would be easier to use a normal rectangle for all sprites . Just focus on putting the genie on the screen and moving it the way you want , Then you can replace the rectangle with beautiful artwork .

The following is the beginning of our player wizard ：

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

We have chosen for players 50x40 Pixel size , And its rect Locate at the bottom center of the screen . We also created a speedx attribute , Used to track players in x Direction （ about ） Moving speed of . If you are not sure about these operations , Please refer to the previous use Elvish Course .

For our Sprite Of update() Method , That is, the code that will be executed in every frame of the game , We want to move at any speed Sprite：

    def update(self):
        self.rect.x += self.speedx

Now? , We can generate our elves , To make sure we see it on the screen ：

all_sprites = pygame.sprite.Group()
player = Player()
all_sprites.add(player)

Don't forget it , Every sprite you create must be added to all_sprites In the group , To update and draw it on the screen .

motion / control

This will be a keyboard controlled game , So we want players to press Left or Right Arrow keys move （ If you will , You can also use a and d）.

When we consider using buttons in games , That means we need to talk about event ：

• Options 1： In our event queue , We can define two events （ One for each key ）, Each event will change the player's speed accordingly ：

    for event in pygame.event.get():
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_LEFT:
                player.speedx = -8
            if event.key == pygame.K_RIGHT:
                player.speedx = 8

The problem with this approach is , Although pressing the key will make the player move , But I can't stop ！ We need to add two more KEYUP event , Set the speed back 0.

• Options 2： We tell sprite Throughout Set its speed to 0 , Unless LEFTor RIGHT Key pressed . This will make the player sprite move more smoothly , And simpler coding ：

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

take speedx Each frame is set to 0, then pygame.key.get_pressed() Check whether the key is pressed . It will generate a dictionary for each key on the keyboard , Its value is True or False Indicates whether the key is currently pressed or lifted . If any key we want is pressed , We will set the speed accordingly .

Stay on the screen

Last , We need to make sure our Genie doesn't leave the screen . We will show players the spirit of update() Method to add the following ：

        if self.rect.right > WIDTH:
            self.rect.right = WIDTH
        if self.rect.left < 0:
            self.rect.left = 0

Now? , If rect Move to the left or right edge of the screen , It will stop . Another option is to surround the screen - When it hits the edge, it transmits the spirit from one side to the other - But for this game , It's more suitable to stop at the edge .

Conclusion

Here is the complete code for this step ：

# KidsCanCode - Game Development with Pygame video series
# Shmup game - part 1
# Video link: https://www.youtube.com/watch?v=nGufy7weyGY
# Player sprite and movement
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

all_sprites = pygame.sprite.Group()
player = Player()
all_sprites.add(player)

# 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()

In the next lesson , We will add some enemy elves for players to avoid .

The first 2 part ： enemy sprite