pygame - Making Asteroids Game in Python-Whats wrong with it? -

here source code asteroids game. used tutorial http://comp4431.wordpress.com/2010/08/11/tut-wk-3-asteroids/ followed closely could. besides of missing fetures fire, wrong it? wont display starmap. btw - new python

import pygame, random, math pygame.locals import * math import *  winflags=0 screenrect=rect(0,0,800,600) #screen res nstars=100 nasteroids=10  #colors black=(0,0,0) white=(255,255,255) yellow=(255,255,0) transparent=(1,2,3)  clock=pygame.time.clock() while true:         clock.tick(30)  class player(pygame.sprite.sprite):      color=yellow     thrust_value=1.0     turn_speed=5     max_speed=10.0      base_image=pygame.surface((21,11))     base_image.fill(transparent)     base_image.set_colorkey(transparent)     pointlist=[(0,0),(0,10),(20,5)]     pygame.draw.polygon(base_image,color,pointlist)      def __init__(self):             pygame.sprite.sprite.__init__(self)              self.image=self.base_image.copy()              self.rect=self.image.get_rect(center=screenrect.center)              self.vx=0             self.vy=0             self.angle=0      def update(self):             self.rect.move_ip(self.vx,self.vy)             self.wrap()      def wrap(self):             if (self.rect.center[0]<0):                     self.rect.move_ip(screenrect.width,0)             elif (self.rect.center[0]>=screenrect.width):                     self.rect.move_ip(-screenrect.width,0)             if (self.rect.center[1]<0):                     self.rect.move_ip(screenrect.height,0)             elif (self.rect.center[1]>=screenrect.height):                     self.rect.move_ip(0,-screenrect.height)      def thrust(self):             a=radians(self.angle)             self.vx+=self.thrust_value*cos(a)             self.vy+=self.thrust_value*sin(a)              vel=sqrt(self.vx*self.vx+self.vy*self.vy)             if (vel>self.max_speed):                     self.vx=self.vx*self.max_speed/vel                     self.vy=self.vy*self.max_speed/vel      def turn(self,direction):             self.angle+=self.turn_speed*direction             while (self.angle<0):                     self.angle+=360             while (self.angle>=360):                     self.angle-=360              self.image=pygame.transform.rotate(self.base_image,-self.angle)             self.rect=self.image.get_rect(center=self.rect.center)      def fire(self):             print 'fire'  class asteroid(pygame.sprite.sprite):      color=yellow     min_speed=2     max_speed=6      base_image = pygame.surface((40,50))     base_image.fill(transparent)     base_image.set_colorkey(transparent)     pointlist=[(10,0),(30,0),(40,15),(35,25),(20,50),(5,50),(0,25)]     pygame.draw.polygon(base_image,color,pointlist)      def __init__(self):             pygame.sprite.sprite.__init__(self)              self.image=self.base_image.copy()              x=int(screenrect.width*random.random())             y=int(screenrect.height*random.random())             self.rect=self.image.get_rect(center=(x,y))              velocity=random.randint(self.min_speed, self.max_speed)             angle=2.0*pi*random.random()#radians             self.vx=cos(angle)*velocity             self.vy=sin(angle)*velocity      def update(self):             self.rect.move_ip(self.vx,self.vy)             self.wrap()      def wrap(self):             if (self.rect.center[0]<0):                     self.rect.move_ip(screenrect.width,0)             elif (self.rect.center[0]>=screenrect.width):                     self.rect.move_ip(-screenrect.width,0)             if (self.rect.center[1]<0):                     self.rect.move_ip(0,screenrect.height)             elif (self.rect.center[1]>=screenrect.height):                     self.rect.move_ip(0,-screenrect.height)  def main():     #init python     pygame.init()      #create window     screen=pygame.display.set_mode(screenrect.size,winflags)      #starmap     background=pygame.surface(screenrect.size)     background.fill(black)     in range(0,nstars):             x=random.randint(0,screenrect.width-1)             y=random.randint(0,screenrect.height-1)             pygame.draw.circle(background,white,(x,y),0)      #blit screen     screen.blit(background,(0,0))      pygame.display.update()      player=player()      render=pygame.sprite.renderupdates()     render.add(player)      asteroids=pygame.sprite.group()     in range(0,nasteroids):             asteroid=asteroid()             render.add(asteroid)             asteroids.add(asteroid)      while true:             event in pygame.event.get():                     if event.type == quit or \                     (event.type == keydown , event.key == k_escape):                       return             keystate=pygame.key.get_pressed()             if (keystate[k_up]):                     player.thrust()             direction=keystate[k_right]-keystate[k_left]             if (direction !=0):                     player.turn(direction)             if (keystate[k_space]):                     player.fire()             asteroid in pygame.sprite.spritecollide(player,asteroids,false):                     asteroid.kill()      render.update()     render.clear(screen,background)     dirty=render.draw(screen)     pygame.display.update(dirty)  #run main() if __name__=="__main__": main() 

these statements update display should inside main loop, instead of after it.

render.update() render.clear(screen,background) dirty=render.draw(screen) pygame.display.update(dirty) 

also, i'm surprised program given infinite loop near beginning

while true:     clock.tick(30)