A Particle

Part of the Sound and Game Feel section of Coddy's Pygame journey. Lesson 8 of 23.

Sparks, dust, smoke and confetti are made of particles: many tiny things that fly out, live a short while and vanish. One particle needs only a few numbers: where it is, how far it moves each frame, and how many frames it has left to live. A dictionary holds them:

{"x": 240, "y": 180, "vx": 2, "vy": -3, "life": 30}

vx and vy are its velocity: 2 pixels right and 3 up each frame. Keep every particle in one list, and each frame move them all and take one frame off their life:

for p in particles:
    p["x"] += p["vx"]
    p["y"] += p["vy"]
    p["life"] -= 1

Draw each particle while its life is above 0, as a small circle:

for p in particles:
    if p["life"] > 0:
        pygame.draw.circle(screen, (255, 160, 60), (p["x"], p["y"]), 3)

A particle has no image and no class. It is cheap, so a game can have hundreds at once.

Challenge

Easy

Make the grey emitter at the middle shoot a spark:

When Space is pressed, append {"x": 240, "y": 180, "vx": 2, "vy": -3, "life": 30} to particles.
Each frame, move every particle by its vx and vy, and lower its life by 1.
Draw each particle whose life is above 0 as an orange (255, 160, 60) circle of radius 3.

Try it yourself

import pygame

pygame.init()
screen = pygame.display.set_mode((480, 360))
pygame.display.set_caption("Sparks")
clock = pygame.time.Clock()

particles = []

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

    screen.fill((30, 30, 46))
    pygame.draw.circle(screen, (120, 120, 140), (240, 180), 8)
    pygame.display.flip()
    clock.tick(60)

pygame.quit()