Many of the film's action sequences revolve around Summer Glau's martial arts skills in her portrayal of River. Glau prepared for her role with Hong Kong stuntwoman Ming Lu, as well as stunt coordinators Chad Stahelski and Hiro Koda, and as a resulted performed nearly all the stuntwork herself. In addition to the stellar stunts, realistic graphics, and an often haunting score, the film's actors display a rare chemistry that brings viewers both into their lives and into a possible version of humanity's future.