Great usage of the light theme! I love how the layered light patterns look overall and that your "weapons" are just different form of lights, which is quite a creative twist on the roguelike wave shooter genre.
I think the submarine and camera movement could feel a bit more smooth and "watery" and the different enemy types would need a bit more abilities to really impact gameplay, than just being faster or having more health. Maybe an enemy that absorbs certain lights would be nice?
Overall a really creative execution of the theme - also, "Piu piu piu piu ........"