Awesome game! The feeling of going really fast and bouncing off of things is really great! Once I learned how to gather speed all the levels clicked. If I were you, I would maybe make the spikes a different color but I think they work fine as is too.
As far as bugs go, the right side of the level titles kept getting cut off for me and I got caught inside a wall inside the starting box of atmosphere once. Other than that it worked great!