I liked the game, but I agree with the previous commenter - it lacks scoring system or upgrade system. Right now it's just fun to ride and shoot enemies. But there is no puprpose. Play it 2 or 3 minutes - you don't know how to tell how far apart you are. Maybe adding just a timer with seconds elapsed would make a big difference in the feel of the game,

 P.S. The best thing I liked in the game is the bmbmbmbmbmbm sound of the gun :)