Not entirely sure what is meant to be hard about it, other than the fact the constant drone of the 'wind' or 'traffic' or whatever it is, makes it hard to play more than a few levels without getting a headache.
I enjoy the concept of the game, and the challenge of not squishing stupid kids who run into the road all day long. But a few things could be improved, as Gazwe mentioned, the description and instructions need updating.
Went through the entire game without using my Hero once, I just sent all my units out to fight and left my hero standing as far to the left as I could.
Hero kept dying far too quickly and since the units respawn very fast anyway it didn't matter. Stick it on x3 speed and sit back and wait for victory.
 "Hardest Parking"){kind=icon}
 "CANDY & spiders"){kind=icon}
 "Epic War 5"){kind=icon}