Umm, pardon me for saying, but this game looks unfinished.
There are loasd of bugs that need to be fixed.
For instance, right now i am not actually playing the game, but letting the game play itself by bouncing off of the walls at full speed. The reason i am doing this, is because the last enemy, an enemy which i have killed several times before, is now immune to my bullets...they just pass right through him.
Also, theres only one real thing to do in this game: Go fast and shoot backwards...
Maybe if the momentum was self-sustaining, and you slowed down when drifting, then it would make it more challenging.