starfield.py

"""
 Parallax Starfield Simulation
 by Leonel Machava <leonelmachava@gmail.com>

 Website:  http://codentronix.com
 Facebook: http://facebook.com/codentronix
 Twitter:  http://twitter.com/codentronix
"""
import pygame
from random import randrange, choice

MAX_STARS = 350
STAR_SPEED = 2


def init_stars(screen):
    """ Create the starfield """
    global stars
    stars = []
    for i in range(MAX_STARS):
        # A star is represented as a list with this format: [X,Y,speed]
        star = [randrange(0, screen.get_width() - 1),
                randrange(0, screen.get_height() - 1),
                choice([1, 2, 3])]
        stars.append(star)


def move_and_draw_stars(screen):
    """ Move and draw the stars in the given screen """
    global stars
    for star in stars:
        star[1] += star[2]
        # If the star hit the bottom border then we reposition
        # it in the top of the screen with a random X coordinate.
        if star[1] >= screen.get_height():
            star[1] = 0
            star[0] = randrange(0, screen.get_width()-1)
            star[2] = choice([1, 2, 3])

        # Adjust the star color according to the speed.
        # The slower the star, the darker should be its color.
        color = None  # initialize color to be pep8 compliant
        if star[2] == 1:
            color = (100, 100, 100)
        elif star[2] == 2:
            color = (190, 190, 190)
        elif star[2] == 3:
            color = (255, 255, 255)

        # Draw the star as a rectangle.
        # The star size is proportional to its speed.
        screen.fill(color, (star[0], star[1], star[2], star[2]))


def main():
    # Pygame stuff
    pygame.init()
    screen = pygame.display.set_mode((640, 480))
    pygame.display.set_caption("Parallax Starfield Simulation")
    clock = pygame.time.Clock()

    init_stars(screen)

    while True:
        # Lock the frame rate at 50 FPS
        clock.tick(50)

        # Handle events
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                return

        screen.fill((0, 0, 0))
        move_and_draw_stars(screen)
        pygame.display.flip()

if __name__ == "__main__":
    main()