Most narrative films strive to maintain the illusion of the continuity of time, space, action and completeness with the help of continuity editing. Continuity errors are mistakes in the narrative, visual or sound continuity of a film that occur during shooting or that arise as part of the post production process (see editing). Continuity errors occur relatively frequently due to the fact that films are rarely shot in the order in which they are presented. Most continuity errors are subtle, such as changes in the level of drink in a character’s glass or the length of a cigarette, while others can be more noticeable, such as sudden and drastic changes in the outer appearance of a character (i.e. a change of clothing from one shot to another without explanation). It goes without saying that errors in continuity are highly problematic since they can significantly disturb the illusion of film as an ongoing continuous action. Nevertheless, they can provide a fun pastime for film enthusiasts, who enjoy the challenge of trying to find errors of this type.