#!/usr/bin/env python
"""A simple starfield example. Note you can move the 'center' of
the starfield by leftclicking in the window. This example show
the basics of creating a window, simple pixel plotting, and input
event management"""
import random, math, pygame
from pygame.locals import *
#constants
WINSIZE = [640, 480]
WINCENTER = [320, 240]
NUMSTARS = 150
def init_star():
"creates new star values"
dir = random.randrange(100000)
velmult = random.random()*.6+.4
vel = [math.sin(dir) * velmult, math.cos(dir) * velmult]
return vel, WINCENTER[:]
def initialize_stars():
"creates a new starfield"
stars = []
for x in range(NUMSTARS):
star = init_star()
vel, pos = star
steps = random.randint(0, WINCENTER[0])
pos[0] = pos[0] + (vel[0] * steps)
pos[1] = pos[1] + (vel[1] * steps)
vel[0] = vel[0] * (steps * .09)
vel[1] = vel[1] * (steps * .09)
stars.append(star)
move_stars(stars)
return stars
def draw_stars(surface, stars, color):
"used to draw (and clear) the stars"
for vel, pos in stars:
pos = (int(pos[0]), int(pos[1]))
surface.set_at(pos, color)
def move_stars(stars):
"animate the star values"
for vel, pos in stars:
pos[0] = pos[0] + vel[0]
pos[1] = pos[1] + vel[1]
if not 0 <= pos[0] <= WINSIZE[0] or not 0 <= pos[1] <= WINSIZE[1]:
vel[:], pos[:] = init_star()
else:
vel[0] = vel[0] * 1.05
vel[1] = vel[1] * 1.05
def main():
"This is the starfield code"
#create our starfield
random.seed()
stars = initialize_stars()
clock = pygame.time.Clock()
#initialize and prepare screen
pygame.init()
screen = pygame.display.set_mode(WINSIZE)
pygame.display.set_caption('pygame Stars Example')
white = 255, 240, 200
black = 20, 20, 40
screen.fill(black)
#main game loop
done = 0
while not done:
draw_stars(screen, stars, black)
move_stars(stars)
draw_stars(screen, stars, white)
pygame.display.update()
for e in pygame.event.get():
if e.type == QUIT or (e.type == KEYUP and e.key == K_ESCAPE):
done = 1
break
elif e.type == MOUSEBUTTONDOWN and e.button == 1:
WINCENTER[:] = list(e.pos)
clock.tick(50)
# if python says run, then we should run
if __name__ == '__main__':
main()
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