Thomas McGahee wrote:

> PONG was the very first video game. You have two
> paddles on the screen that are just short vertical
> bars that can be slid up and down.

> If you keep track of average paddle velocity you can use that info to
> give "spin" or "english" to the ball.

  I thought the usual method was simpler - if the ball hits the centre
half of the paddle, it rebounds with the same Y-velocity component, but
if it hits the upper or lower quarter of the paddle, the Y-velocity is
altered in the corresponding direction.  This models a paddle with
chamfered edges.

  Cheers,
        Paul B.