Actor Asa Butterfield has a tough challenge: bringing to life the lead character of one of the bestselling science fiction novels of all time. In Ender's Game, the 16-year-old Butterfield plays Ender Wiggin, a young boy being groomed in Battle School to command the forces of Earth against an alien invasion. During a recent interview with Spinoff Online's Todd Gilchrist, Butterfield discussed the upcoming film and the challenge of relating to and portraying the iconic science fiction character.

"By far the hardest part of my character was the amount of complexity to him," Butterfield said. "I haven't played a character like him. The amount of thought that goes into every single action that he does and every single move that he makes is immense, and I think that level of detail has to come across in the film, because it does so in the book. It's a lot easier to write that than it is to visualize it and portray it in a character. So much goes on behind the eyes, the tiny movements, which give away what you're thinking. I think Gavin [Hood] did a great job capturing that."

Meanwhile, Hailee Steinfeld, who plays Petra Arkanian in Ender's Game, just finished a role as Juliet in a Romeo and Juliet remake, and said one of the biggest challenges for her was being unable to use the physical space.

"I think one of the biggest challenges for me was spending 90 percent of the time in front of a green screen," she told Spinoff. "It was the most amount of time I've ever spent in a green screen. I think going from a period piece [like 'Romeo and Juliet'] where you're taught to take advantage of everything around you because it's so specific, going from that to working in front of a green screen where you have nothing except your imagination allows you to use it in a way I'd never hoped before. So that was something I really enjoyed."

Check out the full video interviews below.

Directed by Gavin Hood, Ender's Game opens Friday nationwide.