Watching “Tron: Legacy” is like witnessing a thermonuclear explosion from inside the mushroom cloud — white hot, dazzlingly intense and indescribably overpowering. Pure, unblemished spectacle, “Tron: Legacy” is cinematic escapism at its most thrilling and satisfying — pop art unlike any you’ve ever seen before.

The story works as a long-delayed sequel: Sam Flynn (Garrett Hedlund) is the headstrong but ultimately directionless billionaire son of Kevin Flynn (Jeff Bridges), the Encom CEO who vanished mysteriously when Sam was just a young boy. When his father’s friend and colleague, Alan Bradley (Bruce Boxleitner), informs Sam that he received a page from his father’s long-abandoned arcade, Sam investigates, stumbling across a secret lab.

When he tries to hack the system, Sam is zapped into a futuristic cyberworld where he is forced to engage in gladiatorial combat by the dictator Clu, who looks exactly like his father. Rescued by the beautiful Quorra (Olivia Wilde) and the real Kevin Flynn, who has been trapped on The Grid for decades, a reunited father and son undertake a life-and-death journey through a treacherous world toward an exceedingly improbably escape.

The first “Tron,” which hit screens in 1982, was too far ahead of its time for its own good (think “The Matrix” for the Atari generation). The film’s groundbreaking, psychedelic effects (it was among the first films to utilize CGI) look preposterously antiquated now, but, if filtered through younger eyes, still have the power to astonish.

This follow-on expands on the original’s themes and mythology, employing a poignant metaphysical dimension the first film lacked. That much of the narrative is incomprehensible is unfortunate, if ultimately irrelevant. While we’d certainly prefer our story to match our visuals, a metaphysical treatise is not what we came to see.

We came to see a geography constructed of glossy contours, geometric shapes and translucent textures. We came to see vehicles that race on ribbons of light and end their lives in splashes of orange magma. We came to see muscular bodies poured into sexy, jet-black, self-illuminating foam-latex bodysuits.

It is a world of unbounded dimensions, choreographed so that we are never at a loss for geography or spatial depth. With the unfortunate exception of a less-than-successful performance-capture experiment to breathe life into a younger, digital version of Bridges, the effects are better than anything on screen this year. Daft Punk’s cutting-edge score is a flawless compliment to the visuals, music that throbs in your gut and vibrates in your bones.

Commercials director Joseph Kosinski has created a world at once intimately recognizable yet breathtakingly new, a universe every bit as immersive as “Avatar” and one of the very few films to make the most of both the IMAX and 3D technologies. It’s as if we’re seeing this incandescently imaginative, gloriously self-indulgent, fetishistic world for the very first time, and it is dumbfoundingly spectacular.

“Tron: Legacy”

Cast: Jeff Bridges, Garrett Hedlund, Olivia Wilde, Bruce Boxleitner, Michael Sheen

Director: Joseph Kosinski

Rated: PG (for sequences of sci-fi action violence and brief mild language)

Running time: 2 hours, 5 minutes

Photo by TMS