Thanks for the feedbacks!
I think i will try to keep the wall ride idea for a special road block, but effectively, the walls are too much punishing (i have an idea for fixing this, but it is hard to explain with text).
I will add more obstacles/roads (like roads without walls for bigger areas), i will add arrows to the force direction of boosters and a controls tab in the menu!
(sorry if my english is bad, i have to perpetuate the french tradition XD)