The following code moves a ball across the screen at a rate of dx in the x direction and dy in the y direction. ... what do we need to add to line 19 to have the ball bounce off the top of the window like this:
a) Check for collision with the top of the window and reverse the y direction
b) Increase the value of dy
c) Decrease the value of dx
d) Add a statement to pause the ball's movement when it reaches the top
