###################################################################
#
# graphics3.py
#
# Started in Pascal by Jeff Ondich on 1/25/95
# Ported to C++, Java, and Python
# Last modified 1/19/07
#
# 1. Try it.
#
# 2. How can you slow down or speed up the motion of the ball?
#
# 3. The sleep function seems to have a minimum resolution--for
#    example, I don't see a difference between the speed at 0.01 and
#    and 0.005.  Is there something you can change in the step()
#    method to speed up the animation?
#
# 4. Try to get the ball to bounce from side to side instead
#    of up and down.
#
# 5. Can you get the colors to change gradually from red to blue
#    and back instead of abruptly?
#
###################################################################

import time
from graphics import *

class BouncingBall:
    def __init__(self, x, y, radius, window):
        self.window = window
        self.goingDown = True
        self.downColor = color_rgb(200, 10, 60)
        self.upColor = color_rgb(60, 60, 200)
        self.circle = Circle(Point(x, y), radius)
        self.circle.setFill(self.downColor)
        self.circle.draw(window)

    def step(self):
        windowHeight = self.window.getHeight()
        windowWidth = self.window.getWidth()
        x = self.circle.getCenter().getX()
        y = self.circle.getCenter().getY()

        if self.goingDown:
            dy = 2
        else:
            dy = -2

        if y + dy >= windowHeight - self.circle.getRadius():
            self.goingDown = False
        elif y + dy <= self.circle.getRadius():
            self.goingDown = True

        if self.goingDown:
            self.circle.setFill(self.downColor)
        else:
            self.circle.setFill(self.upColor)

        self.circle.move(0, dy)


# First, create a window with a white background.
windowWidth = 650
windowHeight = 500
window = GraphWin('Bounce', windowWidth, windowHeight)
window.setBackground(color_rgb(255, 255, 255))

# Create a BouncingBall object with the specified position and size,
# and associate it with the window created above.
ball = BouncingBall(windowWidth / 2, 50, 50, window)

# Until the user kills the program with a Ctrl+C, move the ball
# one step, wait for a bit, move the ball another step, wait, etc.
print 'Type Ctrl-C in the terminal window to make the animation stop.'
while True:
    ball.step()
    time.sleep(0.02)