What is the computer game called where spaceship/cars make walls to try and make other cars run into them?

i played a game where spaceship/cars made walls to try and make the other cars run into to win the game in my computer class. i cant remember the name but it started with a z. please help, thanks(:What is the computer game called where spaceship/cars make walls to try and make other cars run into them?
Tron?? maybe