Attached find a program I like to call the cannonball game. It is a very basic game, my first attempt at something like this, and I have a few questions.

1) How can i prevent the user from moveing the Target (the Box) off of the line?
2) When you hit the target, then hit fire again, it displays the message that you won again... why?
3)How would I draw a line outlinging the arc of the ball's flight?


Thanks for your help, i'm sure there will be more questions later.