(CNN) More heartwarming than heartbreaking, "Bright Lights" is a touching tribute to the powerful attachment between Carrie Fisher and Debbie Reynolds, a mother and daughter who, in their love for and gripes about each other, clearly left very little unsaid.

HBO took the very it-is-TV-like step of moving the documentary's airdate up in the wake of the two actresses' one-day-apart deaths, seemingly to capitalize on all the media attention. But this 94-minute film, directed by Alexis Bloom and Fisher Stevens, is so lovely, life-affirming and filled with memories that given the grief expressed by fans, it feels more like a public service than crass commercialism.

Showcasing Fisher's rapier wit throughout, the movie opens with the star chatting with her famous mom, as home movies of Fisher as a beaming child unspool across the screen. "You knew that I was going to doubt it later so you filmed me being happy," Fisher groans.

What follows is a highly emotional and oddly universal look at the relationship between a grown-up kid and her aging mom -- a kind of love story, thanks to the intensity of their connection, magnified by their under-the-microscope lives.

The two lived next door to each other, with Reynolds enduring her daughter's playful sniping, but Fisher also exhibiting the sort of protectiveness that takes root when roles are flipped and the child becomes the parent. (Fisher's brother Todd is also prominently featured and one of the film's producers.)

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