This is a small little cabin, where you walk in, and there are two buttons. ON and OFF. The ON button causes Pistons to push up glowstone behind a window of glass to light up the room. The OFF pushes (THIS IS WHERE THE IMPORTANT PART IS) not just the glowstone, or you would still actually see it. It also pushes regular stone that plugs up the glass, cutting out light in the room. I made this small, so you can break it, look at it, study it, or attach it to a room. It is as small as I could possibly make it. So enjoy :D