The camera angles and movements used to depict dream sequences enable this kind of play and confusion between the diegetic reality and the dreamed world by presenting the dream world as a visually accessible space in which the character moves around the same as he does in the diegetic reality, as opposed to restricting themselves cinematographically to a subjective viewpoint even though dreams are generally understood to be experienced by the dreamer from their own subjective point of view. This point is made salient by the films which choose to employ first-person camera angles such as "Strange Days" (1995) when it depicts recorded memories experienced via the "SQUID" recorder, the first-person sequence of "Doom" (2005), the beginning of "Enter the Void" (2010), and others, and how radically these moments stand out against normal cinematography even when the subject matter is something as subjective as a dream. Many have cited the general impracticality and unattractiveness of sustained first-person perspective in film as a reason for its absence from filmed dream sequences. The dream sequence that Atossa narrates near the beginning of Aeschylus' Athenian tragedy "The Persians" (472 BCE) may be the first in the history of European theater. The first dream sequence in a film is more contested. Film critic Bob Mondello claims that the first famous movie with a dream sequence was Buster Keaton's "Sherlock Jr." (1924). Predating this, Leslie Halpern claims the earliest dream sequence was in Edwin S. Porter's "Life of an American Fireman" (1903). Earlier than either of these, James Walters points out G.A. Smith's use of a dream sequence in "Let Me Dream Again" (1900), but is careful to note the precariousness of claiming any film the first to feature a dream sequence given the rapid transnational development of cinema in its early years and that so many films from the period have been lost. Walters traces the dream sequence technique of revealing one thing to be another (revealing what the audience thought was a dream to actually be reality), back to magic lantern shows features "slipping" or "slipper" slides in which; some lantern slides for examples would feature two sheets of glass with different images painted on each, say a cocoon and a butterfly. The first sheet would be projected and then the second sheet slid on top of it to reveal a change, such as a butterfly emerging from a cocoon. Dream sequences became very popular in the early period of film following this change of phase format.