# Ball Fountain for CodeSkulptor3
# with acknowledgements to James Brown
# http://codepen.io/jsbrown/pen/nqDIp

import random, simplegui

# dimensions of screen are in pixels
width  = 200
height = 200

numBalls = 5
radius = 5
gravity = 0.02

class Ball:
  def __init__(self, colour):
    # set initial position and velocities
    self.reset()
    # colour is the ball number from 0 to numBalls - 1
    self.col = 'hsl(' + str(360*colour//numBalls) + ', 100%, 50%)' # colour

  # reset position and velocities, but keep colour
  def reset(self):
    self.x = width // 2                    # x centred
    self.y = height                        # y bottom of screen
    self.vx = random.random() *  1.4 - 0.7 # horizontal velocity left or right
    self.vy = random.random() * -2   - 1.2 # vertical velocity up

# Handler to draw on canvas
def draw(canvas):

  for b in balls:
    # move
    b.vy += gravity
    b.x += b.vx
    b.y += b.vy

    # canvas.draw_circle(center_point, radius, line_width, line_color, fill_color)
    canvas.draw_circle([b.x, b.y], radius, 1, b.col, b.col)

    if ( b.x - radius > width or
         b.x + radius < 0 or
         b.y - radius > height or
         b.y + radius < 0
       ):
        b.reset()  # move back to start
        # colour stays the same

def init():
  global balls
  balls = []
  for n in range(numBalls):
    balls.append(Ball(n)) # n is used to set the colour

def main():
  # Create a frame and assign callbacks to event handlers
  frame = simplegui.create_frame("Fountain", width, height)
  frame.set_canvas_background('white')
  frame.set_draw_handler(draw)

  init()

  # Start the frame animation
  frame.start()

main()