To be honest there's not a lot you really can do AI-wise with such a simple game like pong.
There's only one rule as far as the coputer controlled paddle is concerned - always move the NPC paddle on the Y axis towards the ball's Y position.
Because the computer can do this instantly, the only real control you have is the speed at which this happens. Limiting the speed is more of a 'difficulty level' thing rather than AI though.
As you suggest, not getting the settings right can result in an un-beatable computer opponent. To do this, I think the balance has to be struck in the playability area - not AI.
The key to this is ball speed, paddle speed and ball angle.
As the game progresses, the rate of movement for the ball and both paddles increases gradually, but there also needs to be a method of altering the ball angle and speed according to the speed of the paddle when the ball is struck.
This is the only real way to ensure that it's possible to get the ball moving faster along the Y axis than the computer can reach at it's maximum speed.
This would at least ensure that you don't get an unwinnable game.
Finally, this has told me that I need to update my tutorial to cover this aspect, so thanks for that!
TDK_Man
