Cool game, the trace line on the bullets is a nice touch for aiming. 

I'm not sure why, but when I run it, I hear music and only see a gray window. 

Cute little game :) but the feeling of shooting yourself became redundant pretty fast, So after wave 2 I did not shoot anything myself any longer but just upgraded a turret to shoot at a rate of -0.10/s :D which is pretty damn fast. But I like the idea of the game, it just needs a bigger challenge to it. Good job.

very nice game dude well done