Not, bad, but would be much better if you could control which color ammo you're using, I kept having to let tens of enemies go by unscathed because the game refused to switch to the effective type of ammo, or having to dodge to survive only to have the ammo change after I changed lanes resulting in my death.
Simple, yet challenging. Music goes good with the game. The controls are very responsive. The graphics are simple. Overall, I think it is a good game.