click on the "play" button to start the ball moving.
click on the "stop" button to stop the ball.
this is an example of a pong-like game that has some problems.
for example, to mention a few:
- use the up-arrow and down-arrow keys to move the paddle up and down. but be careful---you can move it beyond the boundaries of the arena...
- the scoring doesn't work. it counts how many times the ball hits the paddle, instead of
counting how many times the opponent misses the ball.
- oh, and there is no opponent...
- the ball only moves horizontally...