Roller Coaster Emotions in Battle Over Amusement Park What goes up didn't have to come down for good, but as Amy Nicholson's "Zipper: Coney Island's Last Wild Ride" shows, the classic high-flying attractions of Coney Island were no match for politicians and developers. Another in a line of gentrification documentaries, from "Foreign Parts" to "My Brooklyn," "Zipper" recounts the contraction and conversion of Coney Island through a medley of voices: amusement-park old-schoolers, protesters, New York City officials and one real estate magnate. The Zipper ride of the title acts as mascot and bellwether in the film. Frequently playing official statements over democratic shots of a thriving Coney Island in its old form, Ms. Nicholson pushes the contrasts between the working-class ride operators and the jargon-spewing officials, between broad access and targeted development, between culture and branding. A comical figure emerges in the unctuous developer Joseph Sitt, who does his interview in front of a statue of a horse. But Mr. Sitt rapidly seems less amusing, as his corporate-minded plans for his Coney Island holdings gradually align with those of the city, prioritizing new businesses and hotels to achieve the area's "unfulfilled potential." Though not terribly nuanced, a bit muddled and lacking certain perspectives, "Zipper" drives home the fragile identity of even the city's signature locales and the alarming cultural myopia of much redevelopment, especially on the part of Mayor Michael R. Bloomberg, Mr. Sitt and Councilman Domenic M. Recchia Jr. (here cast as Judas). This is old news, but Ms. Nicholson suggests that it's not the unambiguously good news of progress hawked by powerful proponents.