In Zombie Highway our goal is to survive the zombie menace infesting the road we are driving through. We'll take advantage of our skill on the wheel and the huge weaponry we'll unlock.
While we'll be driving, those zombies will jump in the car and they'll get hooked to the sides of the car. Then, we'll have to get rid of them. There are two ways to get rid of them: firing using our weapons or passing by other cars and smashing the zombies against those cars and obstacles.
It's very funny and exciting. It's extremely addictive and perfect to play for a short while or to be hours driving. Furthermore, once you crash, you instantaneously think 'I can do it better' and that means you can be playing for hours.
As long as you play, you'll unlock new vehicles, modes and weapons, so the game is not always the same, you'll always have a reason to play it.
Finally, the game is for iPhone, iPod and iPad and has a good list of achievements in Game Center.