Basic information:
It is possible to play this game with a second player, who plays with different buttons, or against the computer who is available in 4 difficulties.
1 Fail = 10 points for the other player.
100 points = win.
After 1 failless minute, sudden death will occur and no player will be able to move until someone scored.
The angle of the ball can be slightly controlled by moving your paddle in a direction while hitting the ball.
It is possible to choose one out of nine midis to play with.
After each game, you will be send back to the menu. It is not possible to save, because this is pong and there's nothing to save

Controls for the Left player / the Blue paddle:
Ex1 for left. (press to grab item in item grab mode)
Ex2 for down. (hold to move the paddle down)
Ex3 for up. (hold to move the paddle up)
Ex4 for right. (press or hold to shoot with the beam-shooting item)
If you play alone, the blue paddle is controlled by the computer, so you don't need the Ex keys.

Controls for the Right player / the Yellow paddle:
Left key for left. (press or hold to shoot with the beam-shooting item)
Down key for down. (hold to move the paddle down)
Up key for up. (hold to move the paddle up)
Right key for right. (press to grab item in item grab mode)

Game modes:
No Item mode is playing a normal pong game without items.
Ball Item mode is playing with items, that randomly appear on the stage. In this mode, the ball changes it's color depending on wich player hit it the last time. The color of the ball then decides who gets the item when the ball touches it. The white ball destroys items, it does not collect them. In this mode it is more based on luck who gets items.
Grab Item mode is playing with items that randomly appear on the stage. In this mode however, items must be grabbed by the players in order to collect them. To grab an item, you must press the grab button while you're in line with an item. Items that are grabbed by a player can't be grabbed by the other one, so whoever's reaction is faster grabs the item. Left player grabs with the Ex1 key and right player grabs with the Right key.

Item list:

This item gives you 5 extra points.

This item paralyzes your enemy temporarily.

This item makes your enemy invisible temporarily.

This item gives you the ability to shoot ball-reflecting beams for a while. *

This item makes you faster for a while.

This item gives you a one-time shield.

* Left player shoots with the Ex4 key and right player shoots with the Left key.

Update (02 Sep 2013):
You can now choose one of nine midis to play the game with.

Update (07 Sep 2013):
Fixed lots of things and added new features and game modes.

"Pong (marketed as PONG) is one of the earliest arcade video games; it is a tennis sports game featuring simple two-dimensional graphics. While other arcade video games such as Computer Space came before it, Pong was one of the first video games to reach mainstream popularity. The aim is to defeat the opponent in a simulated table tennis game by earning a higher score. The game was originally manufactured by Atari Incorporated (Atari), who released it in 1972. Allan Alcorn created Pong as a training exercise assigned to him by Atari co-founder Nolan Bushnell. Bushnell based the idea on an electronic ping-pong game included in the Magnavox Odyssey, which later resulted in a lawsuit against Atari. Surprised by the quality of Alcorn's work, Bushnell and Dabney decided to manufacture the game." - Wikipedia

The best tip I can give you is to carefully read the entire description.
If you play with a second player, set up yours keys like this:

Ex1 = A, Ex2 = S, Ex3 = W, Ex4 = D.

Think ahead and try to move your pad to where the ball will move to, like the computer on boss difficulty does.
In item grab mode, try not get distracted by the items, don't forget the ball.

Atari and the makers of Pong
Me for making this in ZC and for coming up with the item ideas, graphics and sounds.
Creators of the official original midi pack.
And finally, PureZC, Nintendo and you.