Make a sound when balls collides in Python

Third part of this game made with Python. In previous post we’ve added a second ball. Now we add a sound when the balls collides.

import pygame

# Initialize Pygame and set up the display
pygame.init()
screen = pygame.display.set_mode((640, 480))

# Initialize the mixer and load a sound file
pygame.mixer.init()
collision_sound = pygame.mixer.Sound('ball.ogg')
clock = pygame.time.Clock()
# Set up the first ball's initial position and velocity
x1 = 320
y1 = 240
vx1 = 1
vy1 = 1

# Set up the second ball's initial position and velocity
x2 = 100
y2 = 100
vx2 = 2
vy2 = 2

# Set the balls' radius
radius = 20

# Run the game loop
running = True
while running:
    # Handle user input
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        elif event.type == pygame.KEYDOWN:
            if event.key == pygame.K_LEFT:
                vx1 = -2
            elif event.key == pygame.K_RIGHT:
                vx1 = 2
            elif event.key == pygame.K_UP:
                vy1 = -2
            elif event.key == pygame.K_DOWN:
                vy1 = 2
        elif event.type == pygame.KEYUP:
            vx1 = 0
            vy1 = 0
    
    # Update the balls' positions
    x1 += vx1
    y1 += vy1
    x2 += vx2
    y2 += vy2
    
    # Check if the balls are out of bounds and reverse their velocities if necessary
    if x1 - radius < 0 or x1 + radius > 640:
        vx1 = -vx1
    if y1 - radius < 0 or y1 + radius > 480:
        vy1 = -vy1
    if x2 - radius < 0 or x2 + radius > 640:
        vx2 = -vx2
    if y2 - radius < 0 or y2 + radius > 480:
        vy2 = -vy2
    
    # Check if the balls collide and reverse their velocities if necessary
    dx = x1 - x2
    dy = y1 - y2
    distance = (dx ** 2 + dy ** 2) ** 0.5
    if distance < 2 * radius:
        vx1, vx2 = vx2, vx1
        vy1, vy2 = vy2, vy1
        collision_sound.play()  # Play the collision sound
    
    # Draw the balls and update the display
    screen.fill((0, 0, 0))
    pygame.draw.circle(screen, (255, 255, 255), (x1, y1), radius)
    pygame.draw.circle(screen, (255, 255, 0), (x2, y2), radius)
    pygame.display.flip()
    clock.tick(60)