Week 2: Building Interactive Games

Class 3: Game Physics and Movement

3.1 Understanding Game Physics

Game physics involves simulating real-world physics to make games more realistic and engaging. Basic physics principles like velocity, acceleration, and gravity can make movements and interactions in a game feel natural.

3.1.1 Velocity and Acceleration

Velocity is the rate of change of an object's position.
Acceleration is the rate of change of velocity.

Example: Basic Movement with Velocity

import pygame

# Initialize Pygame
pygame.init()

# Screen setup
screen = pygame.display.set_mode((800, 600))
pygame.display.set_caption("Basic Movement with Velocity")

# Colors
white = (255, 255, 255)
black = (0, 0, 0)

# Player setup
player = pygame.Rect(375, 275, 50, 50)
velocity = pygame.Vector2(0, 0)

# Main game loop
running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    # Keyboard input for movement
    keys = pygame.key.get_pressed()
    if keys[pygame.K_LEFT]:
        velocity.x = -5
    elif keys[pygame.K_RIGHT]:
        velocity.x = 5
    else:
        velocity.x = 0

    if keys[pygame.K_UP]:
        velocity.y = -5
    elif keys[pygame.K_DOWN]:
        velocity.y = 5
    else:
        velocity.y = 0

    # Update player position
    player.move_ip(velocity)

    # Clear screen
    screen.fill(white)

    # Draw player
    pygame.draw.rect(screen, black, player)

    # Update display
    pygame.display.flip()

pygame.quit()

3.1.2 Gravity Simulation

Gravity adds realism to games by pulling objects downwards, simulating the effect of gravity on Earth.

Example: Adding Gravity to a Falling Object

import pygame

# Initialize Pygame
pygame.init()

# Screen setup
screen = pygame.display.set_mode((800, 600))
pygame.display.set_caption("Gravity Simulation")

# Colors
white = (255, 255, 255)
black = (0, 0, 0)

# Object setup
object = pygame.Rect(375, 50, 50, 50)
gravity = 0.5
velocity_y = 0

# Main game loop
running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    # Apply gravity
    velocity_y += gravity
    object.y += velocity_y

    # Reset object position if it falls off-screen
    if object.y > 600:
        object.y = 50
        velocity_y = 0

    # Clear screen
    screen.fill(white)

    # Draw object
    pygame.draw.rect(screen, black, object)

    # Update display
    pygame.display.flip()

pygame.quit()

3.2 Bouncing and Reflecting Objects

To create dynamic games, it's often necessary to simulate bouncing objects, such as a ball rebounding off walls.

Example: Bouncing Ball Simulation

import pygame

# Initialize Pygame
pygame.init()

# Screen setup
screen = pygame.display.set_mode((800, 600))
pygame.display.set_caption("Bouncing Ball")

# Colors
white = (255, 255, 255)
black = (0, 0, 0)

# Ball setup
ball = pygame.Rect(375, 275, 50, 50)
velocity = pygame.Vector2(4, 4)

# Main game loop
running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    # Move ball
    ball.move_ip(velocity)

    # Bounce off walls
    if ball.left <= 0 or ball.right >= 800:
        velocity.x = -velocity.x
    if ball.top <= 0 or ball.bottom >= 600:
        velocity.y = -velocity.y

    # Clear screen
    screen.fill(white)

    # Draw ball
    pygame.draw.ellipse(screen, black, ball)

    # Update display
    pygame.display.flip()

pygame.quit()

3.3 Mini Project: Bouncing Ball Game

Goal: Create a game where a ball bounces around the screen, changing direction when it hits the walls.

3.3.1 Code Example

import pygame

# Initialize Pygame
pygame.init()

# Screen setup
screen = pygame.display.set_mode((800, 600))
pygame.display.set_caption("Bouncing Ball Game")

# Colors
white = (255, 255, 255)
black = (0, 0, 0)

# Ball setup
ball = pygame.Rect(375, 275, 50, 50)
velocity = pygame.Vector2(3, 3)

# Main game loop
running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    # Move ball
    ball.move_ip(velocity)

    # Bounce off walls
    if ball.left <= 0 or ball.right >= 800:
        velocity.x = -velocity.x
    if ball.top <= 0 or ball.bottom >= 600:
        velocity.y = -velocity.y

    # Clear screen
    screen.fill(white)

    # Draw ball
    pygame.draw.ellipse(screen, black, ball)

    # Update display
    pygame.display.flip()

pygame.quit()

3.4 Exercises

Add Obstacles:
- Introduce stationary obstacles that the ball can bounce off.
Change Ball Color:
- Make the ball change color each time it bounces off a wall.

Class 4: Working with Sounds and Music

4.1 Adding Sound Effects and Music

Sound effects and music are crucial for creating an immersive game experience. Pygame allows you to easily add sound to your games.

4.1.1 Loading and Playing Sounds

To use sound in Pygame, you must first load the sound file and then play it.

Example: Adding a Sound Effect

import pygame

# Initialize Pygame and Mixer
pygame.init()
pygame.mixer.init()

# Load sound effect
bounce_sound = pygame.mixer.Sound("bounce.wav")

# Screen setup
screen = pygame.display.set_mode((800, 600))
pygame.display.set_caption("Sound Effects")

# Colors
white = (255, 255, 255)
black = (0, 0, 0)

# Ball setup
ball = pygame.Rect(375, 275, 50, 50)
velocity = pygame.Vector2(3, 3)

# Main game loop
running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    # Move ball
    ball.move_ip(velocity)

    # Bounce off walls and play sound
    if ball.left <= 0 or ball.right >= 800:
        velocity.x = -velocity.x
        bounce_sound.play()  # Play sound on bounce
    if ball.top <= 0 or ball.bottom >= 600:
        velocity.y = -velocity.y
        bounce_sound.play()

    # Clear screen
    screen.fill(white)

    # Draw ball
    pygame.draw.ellipse(screen, black, ball)

    # Update display
    pygame.display.flip()

pygame.quit()

4.1.2 Background Music

You can also add background music that plays continuously during the game.

Example: Adding Background Music

import pygame

# Initialize Pygame and Mixer
pygame.init()
pygame.mixer.init()

# Load and play background music
pygame.mixer.music.load("background_music.mp3")
pygame.mixer.music.play(-1)  # Loop indefinitely

# Screen setup
screen = pygame.display.set_mode((800, 600))
pygame.display.set_caption("Background Music")

# Colors
white = (255, 255, 255)
black = (0, 0, 0)

# Main game loop
running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    # Clear screen
    screen.fill(white)

    # Update display
    pygame.display.flip()

pygame.quit()

4.2 Triggering Sounds Based on Events

Sound effects can be triggered based on specific game events, such as collisions or player actions.

Example: Sound Memory Game


python
import pygame
import random

# Initialize Pygame and Mixer
pygame.init()
pygame.mixer.init()

# Load sounds
sounds = [pygame.mixer.Sound(f"sound{i}.wav") for i in range(4)]

# Screen setup
screen = pygame.display.set_mode((800, 600))
pygame.display.set_caption("Sound Memory Game")

# Colors
white = (255, 255, 255)
black = (0, 0, 0)

# Generate random sequence of sounds
sequence = [random.choice(sounds) for _ in range(5)]
current_step = 0

# Main game loop
running = True
while running: