import pygame
import random

def run_game():
    
    ## Initialize the pygame submodules and set up the display window.

    pygame.init()

    width = 640
    height = 480
    my_win = pygame.display.set_mode((width,height))

    # We will use the same radius for all balls.
    radius = 20

    # Create a list of balls. Each ball represented as a list
    # of four elements: x, y, x_speed, y_speed.
    balls = []
    for count in range(0,10):
        x = random.randint(0+radius, width-radius)
        y = random.randint(0+radius,height-radius)
        xspeed = float(random.randint(-100,100))/1000
        yspeed = float(random.randint(-100,100))/1000
        ball = [x, y, xspeed, yspeed]
        balls = balls + [ball]


    # clock
    clock = pygame.time.Clock()

    ## The game loop starts here.
    
    keepGoing = True    
    while (keepGoing):

        ## Handle events.

        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                keepGoing = False


        ## Update game objects

        dt = clock.tick()

        # update circle position
        for ball in balls:
            ball[0] = ball[0] + ball[2] * dt
            ball[1] = ball[1] + ball[3] * dt

            if (ball[0] < radius):
                ball[0] = radius
                ball[2] = -1 * ball[2]
            if (ball[0] > width-radius):
                ball[0] = width-radius
                ball[2] = -1 * ball[2]
            if (ball[1] < radius):
                ball[1] = radius
                ball[3] = -1 * ball[3]
            if (ball[1] > height-radius):
                ball[1] = height-radius
                ball[3] = -1 * ball[3]
        

        ## Draw picture and update display

        my_win.fill(pygame.color.Color("lightblue"))

        # Draw all balls in the list
        for ball in balls:
            
            pygame.draw.circle(my_win, pygame.color.Color('darkmagenta'), (int(ball[0]),int(ball[1])),radius)

        pygame.display.update()

    ## The game loop ends here.

    pygame.quit()


## Call the function run_game.

run_game()