[racket] universal Pong question

> Obviously, each world needs to report on the position of the paddle
> (left or right) that its player controls, but what about the ball?
> Should I just let the worlds handle that with on-tick, or should I
> check that the ball is in the same spot on both worlds every so often,
> or should I have the universe server control the ball and tell the
> world everything except their own paddle position each time something
> changes?

In terms of generic network programming, you should only send 
non-deterministic events (movement of the paddle) and let the clients 
figure out the movement of the ball.

I would send all paddle movements between clients and an extra message 
for when the ball hits a paddle that contains the position of the paddle 
and ball, to ensure that the other client starts from the right state 
when the ball bounces.