Like many Millennials, Hannah John-Kamen grew up immersed in the cinematic worlds of Steven Spielberg. Now her immersion in his canon of stories is a little more permanent. The British actress, who has appeared in “Black Mirror” and “Game of Thrones,” is one of the stars of Spielberg’s big budget sci-fi flick “Ready Player One,” adapted from Ernest Cline’s 2011 book. John-Kamen, a self-described “huge fan” of the book even before the movie was on her radar, auditioned for a new character created for the film. After sending in a tape, she flew to Los Angeles to meet with Spielberg himself at Amblin Studios. “I was shaking, I was so nervous,” John-Kamen recalls of her first meeting with the acclaimed director. “I went to the washroom and I called my dad — nobody even knew I was in L.A. meeting Steven — and then I told my dad, ‘Hi, Dad, by the way I’m in L.A. about to meet Steven Spielberg,’ and he’s, like, ‘OK. Just look in the mirror, be calm, just enjoy yourself and just be who you are...