Downey, Jr. remains a rightfully cherished smartass figure, having as much a ball with Black’s one-liners as he had in “KKBB,” and he sells Tony’s newfound post-traumatic vulnerability more credibly than the film does.

Iron Man 3 is smart, funny and spectacular.

Black has an instinctive feel for balancing action set-pieces against the passages of soap-opera that are required to make them matter.

Black and his co-screenwriter, first-timer Drew Pearce, have great fun reshuffling the deck, teasing about who might occupy what superhero suit and morphing the story along with identity revelations and expansions of the dramatic horizons; the well-chosen cast members respond in kind with virtually palpable glee.

Black proves the perfect blacksmith, forging smart new tech and scenarios for the swaggering super-genius. If this does turn out to be Downey Jr.’s final solo outing, it’s a very strong exit.