Several reviewers singled out the opening of the Ark as one of the film's best special effects. Knight said the effects artists deserved a "special accolade" for their work. Canby described it as a visual display as "dazzling" as the denouement of Spielberg's "Close Encounters of the Third Kind". Ebert said the truck chase stunt was the best he had ever seen, ahead of those in films like "Bullitt" (1968) and "The French Connection" (1971). Several reviewers noted the film's PG rating—meaning any child could see it unsupervised—was too lenient for such a scary film filled with a variety of on-screen deaths. An intermediate rating between PG and R, PG-13, would not be introduced until 1984, in part a response to the violence of the Indiana Jones prequel, "Indiana Jones and the Temple of Doom". Some children were reported to have suffered nightmares afterward.