I will join this contest, sounds fun .
My game will be based on time dilation and black holes/wormholes.
That allows for the animated background to be black holes, the ball will be a star, and the paddles will be giant alien ships.
Here is the preliminary design:
Your "ball" is going to be a star that is going to explode at a certain time. The alien paddles are going to be trying to knock the star over into their opponents quadrants to get the star to explode there. Moving the star back out of the quadrant will expend energy from the ship. The energy controls the reset ability and the shields. When the star explodes then the ship with the weakest shields will be destroyed, or if the ship runs completely out of power then the star will explode in that players quadrant.
The time powerups can accelerate the rates of the ships or cause the decay of the star to speed up/slow down. Other powerups could include energy for the ships.
Difficulties levels can be implemented by using different sizes/speeds of ships for the opponent, changing the speed of the player ship, altering the starting shield strength for the player, and decreasing the amount of time the star has before it explodes.
I will post updates eventually .