Well, it's a clicker game, that you click on a wheel until you reach however far it says up in the top left.
Reason I am rating low is because there isn't much to this. The number in the top left is the amount of times you need to click. 1 click = 1km. I was hoping that since it is a wheel, after awhile it might start to roll itself, but realized that it didn't work like that.
For difficulty, I'd actually call the "easy" difficulty hard, "normal" difficulty dedicated, and the "hard" difficulty impossible. I'd have to imagine after 72,000 clicks on a single tire, some damage would be done to your mouse too.