Cool game, congrats!!
Ways to make it better: the speed of enemies make them blurry, a tad slower and that would be better I think!
Also, it could start with a lower difficulty (sometimes it seems impossible to survive, with many spikes at once =)) and slowly get harder.
A simple animation when dying, followed by a display of the score, to give a better overall pace.
Just ideas, but the game is already very well done. Thx for contributing!!!