Well done! Excellent Game!!
First off, I totally enjoyed the game, nice style, nice original gameplay. Surprising attention to detail as well, like changing the perspective of where the camera sits in the tube, etc. Anyway, two suggestions:
1.) Would it be possible to add shadows or some hints as to where the enemies are in 3d space? it seemed finding where they were took some trial and error
2.) Music didn't make the game entirely engrossing, but it worked.