Move the tennis racket up and down and hit the ball when it will be next to the racket, the later you'll hit the ball the stronger you'll hit it. Remember that it's played on a tennis court so the ball has to bounce within the lines.
You'll be able to play versus the computer or versus a friend. It's a colorful game which offers you a lot of fun. Very simple but effective. Good for children and not so children and really, really addictive. Tennix has revolutionized and powered-up the Pong universe.