'''
Sign your name: Tristan

All questions are about the final code in Chapter 12:

1.) Where is the ball's original location?
(320, 240)
2.) What are the variables dx and dy?
The rate the ball moves in the direction x and direction y.
3.) How many pixels/sec does the ball move in the x-direction?
180 pixels/sec
4.) How many pixels/sec does the ball move in the y-direction?
120 pixels/sec
5.) Which method is run 60 times/second?
update_ball
6.) What does this code do?   self.dx *= -1
It makes the ball change x direction if it hits a wall
7.) What does this code do?  self.pos_y += self.dy
It makes the ball change y direction if it hits a wall
8.) What is the width of the window?
640 pixels
9.) What is this code checking?  self.pos_y > SH - self.rad:
To see if the ball is touching a wall on top.
10.) What is this code checking? if self.pos_x < self.rad
To see if the ball is touching a wall on the sides.
'''