The game relies on repetitions to hide the fact that there's nothing to it. No variety, no skill (unless you call holding the same button a skill), zombies do absolutely nothing and die from even slight touch of your vehicle. Speaking of vehicle, at the end of each level you get a new, "better" vehicle which you have to upgrade again. There's no strategy behind it either - to complete the level you must play it ~50 times and get your car to the max to loose it in the end. Horrifically boring.