I’ve been using this app for many years (since 2013!) to display a burning candle, especially during Christmas Eve candlelight church service, when everyone is singing “Silent Night” while holding candles in the darkened church, but my hands are too busy playing the guitar for them to hold a real flame. It worked on iOS 6 when I first got it, and works fine for me on iOS 11 & 12 on my new iPad Pro.