Python and Pygame: Building a Platformer Game

Overview
Prerequisites
Setup
Step 1: Setting up the Game Window
Step 2: Creating the Player Character
Step 3: Implementing Player Movement
Step 4: Adding Platform Objects
Step 5: Implementing Collisions
Conclusion

Overview

In this tutorial, we will learn how to build a platformer game using Python and the Pygame library. A platformer game is a genre where the player controls a character that jumps between platforms while avoiding obstacles. By the end of this tutorial, you will have a basic platformer game where the player can move and jump, and there are platforms to stand on.

Prerequisites

To follow along with this tutorial, you should have a basic understanding of Python programming language syntax. It would also be helpful to have some familiarity with object-oriented programming concepts.

Setup

Before we start building the game, we need to set up our development environment. We will be using Python and the Pygame library. Here are the steps to get started:

Install Python: Download and install Python from the official Python website: python.org. Choose the appropriate installer for your operating system and follow the installation instructions.
Install Pygame: Open a terminal or command prompt and run the following command to install Pygame using pip:
```
pip install pygame
```
This will download and install the necessary files for Pygame.
Text Editor: Choose a text editor or integrated development environment (IDE) to write your Python code. Some popular choices include Visual Studio Code, PyCharm, and Atom. Select the one that you are comfortable with or prefer.
Create a Project Folder: Create a new folder on your computer where you will store your game project. This will serve as your workspace for the game development.

Now that we have our development environment set up, let’s move on to building our platformer game step by step.

Step 1: Setting up the Game Window

The first step is to set up the game window. This window will serve as the main display for our game. Follow these steps to create a basic game window:

Import the necessary libraries:

import pygame
from pygame.locals import *

Initialize Pygame:
```
pygame.init()
```
Set up the game window dimensions:
```
width = 800
height = 600
window = pygame.display.set_mode((width, height))
pygame.display.set_caption("Platformer Game")
```
Here, we create a window with a width of 800 pixels and a height of 600 pixels. We also set a window caption that will be displayed at the top of the game window.
Set up the game loop:
```
running = True
while running:
    for event in pygame.event.get():
        if event.type == QUIT:
            running = False
```
This code sets up the game loop, which continuously updates the game state and renders the game window. The loop will exit when the user closes the game window.
Update the display:
```
pygame.display.update()
```
This line updates the game window with any changes made in the game loop.

Congratulations! You have set up the game window for your platformer game. You can run the code and see the blank game window appear.

Step 2: Creating the Player Character

Now that we have our game window set up, let’s create the player character. This character will be controlled by the player and will move around the game world. Follow these steps to create the player character:

Create a Player class:

class Player(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface((32, 32))
        self.image.fill((255, 0, 0))
        self.rect = self.image.get_rect()
        self.rect.x = width // 2
        self.rect.y = height // 2

Here, we create a Player class that inherits from the Pygame Sprite class. The player character is represented by a red rectangle (32x32 pixels) as the character’s image. The rect attribute represents the player’s position and size within the game window. We initialize the player’s position to the center of the game window.

Add the player instance to the game loop:
```
player = Player()
all_sprites = pygame.sprite.Group()
all_sprites.add(player)
```
Here, we create an instance of the Player class and add it to the all_sprites group. This group allows us to easily update and draw all the game sprites.
Draw the player on the game window:
```
all_sprites.draw(window)
```
This line should be added inside the game loop, after calling pygame.display.update(). It draws all the sprites in the all_sprites group onto the game window.

By completing these steps, you have created the player character and displayed it on the game window. When you run the code, you should see a red rectangle representing the player character in the center of the game window.

Step 3: Implementing Player Movement

Now that we have the player character displayed on the game window, let’s implement movement controls for the player. Follow these steps to allow the player to move the character:

Add player movement attributes:
```
class Player(pygame.sprite.Sprite):
    def __init__(self):
        # ...

        self.velocity = [0, 0]
        self.speed = 5
```
Here, we add the velocity and speed attributes to the Player class. The velocity represents the player’s current movement speed in the x and y directions. The speed attribute determines how fast the player moves.

Handle keyboard input events:

for event in pygame.event.get():
    if event.type == QUIT:
        running = False
    elif event.type == KEYDOWN:
        if event.key == K_LEFT:
            player.velocity[0] = -player.speed
        elif event.key == K_RIGHT:
            player.velocity[0] = player.speed
        elif event.key == K_SPACE:
            # Implement jumping
            pass
    elif event.type == KEYUP:
        if event.key == K_LEFT or event.key == K_RIGHT:
            player.velocity[0] = 0

Here, we handle the KEYDOWN and KEYUP events to detect when the player presses and releases arrow keys. When the left or right arrow key is pressed, we update the player’s x-axis velocity to move the character left or right. When the arrow key is released, we stop changing the velocity.

Update the player’s position:
```
class Player(pygame.sprite.Sprite):
    def update(self):
        self.rect.x += self.velocity[0]
        self.rect.y += self.velocity[1]
```
Here, we add an update method to the Player class that is called every frame to update the player’s position based on the current velocity. By adding these lines, the player character will move left or right when the corresponding arrow key is pressed.
Call the update method inside the game loop:
```
while running:
    # ...
    all_sprites.update()
```
This line should be added inside the game loop, just before pygame.display.update(). It calls the update method for all the sprites in the all_sprites group, including the player character.

After completing these steps, you should be able to control the player character using the left and right arrow keys. The player should move smoothly across the game window.

Step 4: Adding Platform Objects

Now that we have our player character moving, let’s add some platforms for the player to stand on. Platforms are objects that the player can collide with and stand on. Follow these steps to add platform objects:

Create a Platform class:

class Platform(pygame.sprite.Sprite):
    def __init__(self, x, y, width, height):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface((width, height))
        self.image.fill((0, 255, 0))
        self.rect = self.image.get_rect()
        self.rect.x = x
        self.rect.y = y

Here, we create a Platform class that also inherits from the Pygame Sprite class. The platform’s image is a green rectangle with the specified width and height. The rect attribute represents the platform’s position and size within the game window. We initialize the platform’s position using the provided x and y coordinates.

Create platform instances:
```
platform1 = Platform(0, height - 50, width, 50)
platform2 = Platform(width // 2 - 50, height // 2, 100, 20)
all_sprites.add(platform1, platform2)
```
These lines create two platform instances using the Platform class and add them to the all_sprites group. The first platform spans the entire width of the game window at the bottom, and the second platform is positioned in the middle of the game window.
Draw the platforms on the game window:
```
all_sprites.draw(window)
```
This line should be added inside the game loop, after the player update and before displaying updates. It draws all the sprites in the all_sprites group onto the game window.

By completing these steps, you have added platform objects to the game window. When you run the code, you should see green rectangles representing the platforms that the player character can stand on.

Step 5: Implementing Collisions

Now that we have the player character and platform objects, let’s implement collision detection so that the player can stand on platforms and not fall through them. Follow these steps to implement collisions:

Check for collisions:

class Player(pygame.sprite.Sprite):
    def update(self):
        # ...

        # Check for collisions with platforms
        platform_collisions = pygame.sprite.spritecollide(self, platform_group, False)
        for platform in platform_collisions:
            if self.velocity[1] > 0:
                self.rect.bottom = platform.rect.top
                self.velocity[1] = 0
            elif self.velocity[1] < 0:
                self.rect.top = platform.rect.bottom
                self.velocity[1] = 0

Here, we add collision detection code inside the player’s update method. We use the spritecollide function to check for collisions between the player and the platform group. If there is a collision, we adjust the player’s position and velocity based on the collision direction.

Group the platforms:
```
platform_group = pygame.sprite.Group()
platform_group.add(platform1, platform2)
```
These lines create a separate sprite group for the platforms and add the platform instances to that group.

By completing these steps, the player character should collide with the platforms and stand on them without falling through. You can run the code and test the collision behavior.

Conclusion

Congratulations! You have successfully built a platformer game using Python and the Pygame library. In this tutorial, you learned how to set up the game window, create the player character, implement player movement, add platform objects, and handle collisions.

You can further enhance your game by adding additional features such as enemies, power-ups, and multiple levels. Experiment with different graphics, sounds, and gameplay mechanics to make your game unique.

I hope you enjoyed this tutorial and found it helpful in understanding how to build a platformer game with Python and Pygame. Happy coding!

Published: 23 December 2022