In this editorial, originally printed in Game Developer magazine's September 2010 issue editor-in-chief Brandon Sheffield discusses the importance of mystery in games, and how the unknown gives players the urge to see what lies around the corner.
“Nothing is so frightening as what’s behind the closed door. The audience holds its breath along with the protagonist as she/he (more often she) approaches that door.” So writes Stephen King in his non-fiction book on horror, Danse Macabre.
King was not the first to make this point, nor will he be the last—with the right setting, the closed door, with all its possibilities, can be a frightening thing. Contrast that with an open door with light streaming through it, a traditional symbol of hope.