You can build a game for 2 or 4 players. If you want to create it for 4 players do the optional steps.
Step 1: Create the feet
Made 2 feet in this way.
Step 2: A controller based on color sensor (only for use playing game for four players)
Make it only if you want a game for 4 players.
How it works?
When the sensor is pointing on the green strip, the motor will rotate slowly. else when pointing orange - quickly and if yellow - somwhere in the middle.
Step 3: A controller based on ultrasonic sensor (only for use playing game for four players)
This controller works like the previous controller, as the motor is closer to the front plate, the motor will rotate more slowly.
Note: This step is a bit harder than the previous steps.
Step 4: The program
Game for 2 players: http://www.2shared.com/file/oTK6FRM3/soccerTable.html
Game for 4 players: http://www.2shared.com/file/tbw70328/soccerTable4players.html
Step 5: Connect all together
Connect the touch sensors to ports 1 and 3 with medium cables.
For 4 players:
Connect the ultrasonic sensor with extra-long cable.
Connect the color sensor with short cable.
Step 6: How to play?
One player hold the A motor and the 1 touch sensor. The second player hold the C motor and 3 touch sensor.
The players hold touch sensors & motors like in 2 players game, but the player who played with player A, the color sensor, and the fourth player control the ultrasonic sensor.
In both games you can write the scores with the arrows key on the NXT.