"""A balloon-launch simulation.

This example shows object-oriented design in animation for

defining a set of "actors" (the balls) that parade on stage.

"""

speed(30)

size(340, 482)

# Import PRNG and trigonometry functions

from random import seed

from math import sin,cos

# The main actor in the animation is a Balloon.

# A Ball has a set of state values: its position, size, color and delta-values.

# The delta-values affect the position and size, and are a simple way to give

# each ball "character". Higher delta-values make the ball more hectic.

class Balloon:

# Initialize a ball -- set all the values to their defaults.

def __init__(self):

self.x = random(WIDTH)

self.y = random(HEIGHT)

self.size = random(10, 72)

self.dx = self.dy = self.ds = 0.0

self.color = color(random(), 1, random(0,2), random())

# Update the internal state values.

def update(self):

self.dx = sin(FRAME/float(random(5,100))) * 20.0

self.dy = cos(FRAME/float(random(5,100))) * 20.0

self.ds = cos(FRAME/float(random(5,100))) * 10.0

# Draw a ball: set the fill color first and draw a circle.

def draw(self):

fill(self.color)

arc(self.x + self.dx, self.y + self.dy, self.size + self.ds)

# Initialize the animation by instantiating a list of balls.

def setup(anim):

anim.balloons = []

for i in range(30):

anim.balloons.append(Balloon())

# Draw the animation by updating and drawing each individual ball.

def draw(anim):

background(0.2)

seed(1)

# This translate command makes the ball move up on the screen.

translate(0, HEIGHT-FRAME)

for ball in anim.balloons:

ball.update()

ball.draw()