I like this, and really think it is a great achievement given the 72-hour time constraint.
The lighting / material shader effect is cool, and its utility as a damage indicator helps give the game a dream-like quality, as did the bouncing bullets and the choice of color. The sounds fit the game well, too.
My (small) suggestions would be that instructions might be helpful at the start, and that a damage indicator for enemies might be useful: I had difficulty figuring out how close to death the enemies were.