good idea
I love Line Rider and Stunt Bike is another of my favorites. Mixing these two games was a great idea. But this game loses a lot of what made Line Rider so awesome, and that is the freeform creativity and experimentation. The way that the screen scrolls from one side to the other was a bit hard to handle. I would love to see a version where (like Line Rider) you can draw where you like, put jumps where you like, extend the track as long and as far as you like, etc. and also (like Stunt Bike and this game already is) you can control your lean and acceleration.
Overall, great idea. These were two games that were meant to be married.