The one thing that seems to be consistent about Whedon is his eagerness to subvert genres: vampires in Buffy, sci fi in Firefly, spies in Dollhouse.
http://thefilmexperience.net/blog/2013/10/7/gravity-and-the-limits-of-a-perfect-10.html
http://thefilmexperience.net/blog/2013/10/7/gravity-and-the-limits-of-a-perfect-10.html