Yes, my first question was not clear and I realized it later, I am sorry.
I am going to show with a screen shot:
On this road, to take forward the car, it is necessary to press on a touch of the keyboard which is going to be randomly chosen by the script. Every time the player press the good touch of the keyboard, the car will move forward a little and the player need to do this until the finish line .If the player does not press the good touch, the car will not move forward. It is in a way a game of speed.
And this touch which the player will have to press will be visible with a widget.
I hope to have been clear.
Thanks for your help Everynone.