Ok get your mind out of the gutter. I am talking about the beautiful blue glass bottle that the Bawls soft drink comes in. I tried one the other day and thought the glass bottle could be used for something interesting. At first I was just going to stick an LED into it, but I wanted something a bit more interesting. So I threw together a quick and dirty circuit that uses a photo-cell to turn on a transistor which powers an LED. The parts should cost only 2 or 3 dollars, and are available almost anywhere.