Before its reputation as the greatest film of all time was cemented, and even before it was released, “Citizen Kane” (1941) was a lightning rod. Its first-time director, Orson Welles, already known for his innovations in theater and radio, had gone to Hollywood in his mid-20s riding a wave of anticipation. By making his debut feature a thinly veiled portrait of the newspaper tycoon William Randolph Hearst, he had chosen a target who could guarantee that the film would be shunned in the press. “Kane” hadn’t even opened when Louis B. Mayer, the production chief of M.G.M., hatched a plan to pay off R.K.O., the film’s studio, and have the negative destroyed.

That didn’t happen, and today “Kane” lives on as a near-universally recognized masterpiece. It’s still an active subject of discussion: The new Netflix film “Mank,” about Herman J. Mankiewicz, who shared writing credit with Welles, deals at least partly with the making of “Kane.” But controversy alone doesn’t sustain a movie’s reputation for nearly 80 years. If you’ve watched “Mank” but have never seen “Kane” (which is available to stream or rent on major platforms), here are three examples of what made it revolutionary.

Structure

In the simplest terms, “Kane” is told in flashback beginning with the death of its Hearst stand-in, Charles Foster Kane (played by Welles), who in the first scene is shown uttering a mysterious dying word: “Rosebud.” Then, a sophisticated facsimile of a newsreel provides an overview of Kane’s life, touching on milestones (his sudden wealth in boyhood after his mother acquired a supposedly worthless mine shaft; his first marriage to a president’s niece; the scandal that derailed his gubernatorial ambitions) that cue viewers about what to watch for later, since what follows won’t be strictly linear.

When the newsreel ends, its producer complains it needs an angle. Thompson (William Alland) is assigned to interview people who knew Kane to find out what Rosebud means.

Each new Kane associate prompts a set of flashbacks, and it’s always interesting to look for where the narrating character is positioned within those scenes, which at times emphasize the subjective perspective. The flashbacks are broadly but not strictly chronological, so that the written memories of Thatcher (George Coulouris), the banker who became young Kane’s guardian, can end in 1929, when Kane’s newspaper empire suffers a crash-related setback, and the movie can double back, in a flashback related by Bernstein (Everett Sloane), Kane’s general manager, to his boss’s first day running his first paper. The story of Kane’s second wife, Susan Alexander Kane (Dorothy Comingore), and her disastrous debut as an opera singer is related first by Kane’s friend Jed Leland (Joseph Cotten), and then revisited from Susan’s point of view. Few films have so fluidly intermingled the demands of character and story or shifted perspectives so deftly and economically. Nothing is ever unclear.

Visuals

Welles’s use of shadows and low angles have led some observers to categorize “Citizen Kane” as a film noir. But its most celebrated photographic device is deep focus, a technique that allows the foreground and background to be seen clearly at the same time, and that became closely associated with Gregg Toland, the film’s cinematographer.

For example, a number of deep-focus shots show characters in the foreground discussing Kane’s fate as Kane — oblivious or powerless — is seen in the background. This happens early when Kane’s mother (Agnes Moorehead) signs over custody to Thatcher, and Kane as a child is seen in a distant window playing in the snow. It happens a few minutes (and 58 years) later, in the 1929 scene, when Kane is forced to relinquish ownership of newspapers to Thatcher. When Kane celebrates his complete acquisition of the staff of a rival paper, The Chronicle, Jed questions the newsmen’s loyalty to Kane’s brand of muckraking. “There’s always a chance, of course, that they’ll change Mr. Kane, without his knowing it,” he says to Bernstein, as Kane dances in the background, unaware of their conversation.

Welles was so appreciative of Toland’s contributions that he put the cinematography and directorial credits on the same credit card. But it’s also worth paying attention to the film’s optical effects and editing, particularly its magical transitions. (The editor was Robert Wise, the future director of “The Sound of Music.”) The opening sequence uses a series of dissolves to bring viewers closer and closer to Kane’s lighted room at Xanadu, his sprawling estate. Dissolves that show young Kane’s abandoned sled getting covered in snow end on wrapping paper that contains a new sled, a Christmas present. Later on, a photograph of The Chronicle’s newspaper staff dissolves into the staff being photographed — this time in the employ of Kane’s Inquirer, with Kane suddenly stepping in front of them. In other scenes, such as when a stagehand holds his nose at Susan’s singing, multiple shots have been combined to look continuous.

Sound

It’s also often noted that Welles brought his background in radio with him to the screen, and many of the most memorable leaps in time and location in the film are assisted by an inventive use of sound. “Merry Christmas,” a young Kane says petulantly — before the film cuts to Thatcher saying “and a happy New Year,” reading aloud from a letter he has written to Kane in advance of his 25th birthday. “I’m going to send you to Sing Sing, Sing Sing, Gettys! Sing Sing!” Kane shouts to the political boss Jim Gettys (Ray Collins) — and the words “Sing Sing” are cut off (almost echoed) in the sound of a car horn honking. As reporters in the finale sift through Kane’s belongings, their voices overlap and complement each other in a technique derived from theater and radio. This was also the first film the composer Bernard Herrmann scored, and the foreboding brass and woodwinds over the movie’s first shots portend his future, indelible collaborations with Alfred Hitchcock.