This is my talk about dark UI design. I originally gave it in Los Angeles for World Usability Day 2018, where the theme was "Dark UX." I was invited to share the talk again in 2019, this time at the World Usability Congress in Graz, Austria. In the talk, I explore the sci-fi origins of Dark UI (and the bias inherent in it), where dark UI works, and what the major usability pitfalls are.