Number one daughter told me that I might like to get some of these lights. She’s right. They’re great. The bottom Tetris piece (the blue bar) is connected to a power source and the others then light up when you stack them above. I spent a happy ten minutes getting them into this vaguely plausible arrangement. I’m trying to get them stacked with the top flat… If you are a Tetris aficionado you might want to seek them out.