Tony Stark has had a rough go these last few years: a near-death experience in the Afghan desert, open-heart surgery in a cave, the challenge of keeping a straight face when confronted with Mickey Rourke's Russian accent, and the indignity of sharing the limelight with a bunch of fellow superheroes, one of whom, Hawkeye, nobody has ever heard of.

And now, in Iron Man 3 - after two Iron Mans and The Avengers - Robert Downey Jr.'s billionaire industrialist, a.k.a. the "man in a can," seems on the verge of a nervous breakdown. Sleep-deprived and prone to panic attacks, Stark is spending most of his time tinkering with his collection of armored Iron Men - loads of them, each more advanced than the last. He seems closer with Jarvis, the disembodied A.I. voice (courtesy of Paul Bettany) that oversees Stark's computers, than he does with Pepper Potts (Gwyneth Paltrow), his live-in girlfriend and CEO of Stark Industries.

And then a guy with a pronounced bin Laden vibe - not to mention a bin Laden beard - hacks into the TV networks with viral videos of bombings and assassinations. "Some people call me a terrorist," the Mandarin (Ben Kingsley) observes in preacher-like intonations, eyeballing the camera. "I consider myself a teacher." And then the teacher takes credit for a deadly attack on Hollywood Boulevard's famed Chinese Theater. Is nothing sacred?!

Iron Man 3, directed by the '80s action screenwriter Shane Black (he also directed Downey in 2005's jaunty neo-noir, Kiss Kiss Bang Bang), is a big, kabooming sequel that plays sleight-of-hand with its audience. If the 1999 New Year's Eve sequence that opens the film tells us anything - apart from Downey's rambling voice-over insights about how "we create our own demons" - it's that you should never snub a misshapen supergenius when he asks to show you his plans for a human repair and growth formula. When Tony Stark doesn't keep his promise to meet an excited Aldrich Killian (Guy Pearce) on the rooftop of a Swiss hotel, his fate - Tony Stark's, that is - is sealed.

And so, too, in Iron Man 3, is the fate of the world. Not even the president is safe from the menace of the Mandarin. At one point, it's up to Iron Man to save 13 crew members sucked out of Air Force One at 30,000 feet. Jarvis calculates that the best Iron Man can do is carry four to safety, but that won't do. The alloy-plated hero with the thrusters and repulsors orchestrates a midair Barrel of Monkeys hookup, bringing the plummetees to safety in Miami harbor. It's the most spectacular stunt of the film, all the more so because it was (more or less) real. The climactic CGI stunts on a giant oil rig, involving an army of flying Iron Men, a phalanx of bad guys, and Don Cheadle and Downey leaping from exploding catwalks, pale by comparison. The action plays like a video game because, well, it may as well be.

One of the prime conceits of Iron Man 3 is that Tony Stark must prove himself all over again. Stark's gizmos have been taken away from him, destroyed. It's a test: can he still cut it without his technology, his prehensile armor, his GPS? His Eero Saarinen-like house on a Malibu bluff has been blown to smithereens, and Stark blows across the States, crash landing in a small Tennessee town, on the trail of someone, or something.

A pip-squeak kid (Ty Simpkins) tries chasing an intruder out of his father's shed, only to discover that the intruder is Stark. Soon the boy, Harley, is helping the wiseguy inventor upload this, and downlink that, and amp up the whosie-whats-its. It's a veritable tech-nerd bonding moment.

Rebecca Hall, the British actress, sparks things up as an old flame of Stark's - or old one-night stand (his memory is kind of fuzzy). Pepper's not sure what to make of this Dr. Maya Hansen, a brilliant geneticist. Suffice to say, things get a little tense between the two women. For about five seconds, which is the average down time between explosions and aerial battle sequences in this overblown sequel.

Jon Favreau, who directed the very good Iron Man and the not-so-good Iron Man 2, returns to mere acting - reprising the role of Happy Hogan, Stark's bodyguard and chauffeur, now the security chief for Stark Industries. Hogan has reason to worry, but he also finds a reason to watch Downton Abbey on TV. It's Iron Man 3's saving grace: It still knows how to be funny.

But then the mayhem and the megalomaniacal villainy start again.