Demi Lovato brought fire and ice to the American Idol stage Thursday, performing two singles ? "Confident" and "Stone Cold" ? that explore polar opposite moods. But she toned down the brash vibe with a dynamic powerhouse take on "Stone Cold," the third single from her 2015 LP, Confident. "God knows I tried to feel happy for you / Know that I am, even if I can't understand," she sang over muted piano chords. "We wanted to be extremely interactive with all of the fans, and that comes down to the performances but also the smell when you enter the arena," she said.