There is a flaw that I couldn't help but notice: No manner how fast you can get while moving, your horizontal speed always the same -Whether you are slow to a crawl, or reaching the speed of light.
One of the main reasons why the game would then feel unplayable for some, despite the foward speed feeling (and I personally believe it maybe is) too fast in order to react, is also because the horizontal speed doesn't change to accommodate the faster speed.
Because of this, if you end up too fast, you simply are unable to turn fast enough once you end up colliding into a rock, even if it is for about, lets say... A quarter of a second? Worse, because of how fast you can end up, even if you can see the rock ahead, you simply don't have horizontal speed to avoid it in time.
I know, a bit harsh on the grade, but the game has an interesting premise - The gameplay just needs more polishing, and balancing in my opinion.