What type of curtains?

[Isthiscorrect]

We have a L shaped room with 3 large patio windows. They have mirrored glass, to keep the sun out (we live overseas). The trouble is everyone can see in from the street when the lights are on in the evening. we don't really want curtains as we wouldn't shut them, they would look too heavy and overpower the room IMHO.
I think we need some sort of voile or similar but everything I have seen still shows right into the room.
Any ideas please?