Crimson Skies will fill you with longing. This is a good thing. Its premise is outrageous and fantastic, but it feels just possible enough that we suspend our disbelief fully. We wish the world had turned out like this, so beautiful and so exciting and so full of roguish adventure.

That is enough superlatives for now. Crimson Skies is a what-if game, set in a century that looks and smells like the 20th we just finished, but somehow turned out differently from our own. The back story is that the Great Depression was too much, that there was no New Deal, that the United States collapsed under the weight of the 1930s and fell into civil war. That is not the part you will find yourself longing for.

In the post-USA world, "Hollywood," emerges as a major state power, as do Texas and Utah and something clustered around the Great Lakes called "The Industrial States of America." A new kind of stability settles over the continent. But the fighting was fierce and the ground was dangerous, and now most of the rail and road infrastructure lies in ruins. So the new societies of this new America take to the skies, moving goods and people in great airships.

The cities are full of masts and orderly queues of hovering dirigibles. People dress smartly and talk in zingy one-liners. It as if the world never lost interest in that sleek dreamy Art Deco aesthetic. It is the 1940s, as imagined in the darkest days of 1932. That is the part you will long for: A world that might have been.

Airships look beautiful, of course, and they are a glorious, sophisticated way to travel, but the witty repartée of cocktail hour at 1,500 feet does not make for great video gaming. The solution? Pirates!

At least that is part of the solution. You may recall a game called "Skies of Arcadia" with a similar premise. It too had dirigibles and pirates and failed diplomacy. But it also had terrible writing and that eye-glazing role-playing-game vibe, and it was larded with stupid gimmicks like magic and magic weapons and magic charms. Note to game designers: You do not need magic if you have decent industrial design.

Crimson Skies has fantastic industrial design. The plane you fly first looks like something Billy Bishop might have taken into battle, only sturdier and with its propeller mounted at the rear. This is creatively improbable from an engineering point of view, but it involves considerably less suspension of disbelief than, say, a magic enchanted sword.

You are a pirate named Nathan Zachary. It is your job to steal planes and airships, and to loot anything that flies by. In practical terms this means you spend most of your time in thrilling dogfights, aiming your machine guns and your primitive heat-seeking missiles (again that industrial design) at the other bad guys. Morally the thing is ambiguous as hell. You are, after all, stealing both from thieves and from legitimate property-owners. But you, as Nathan, have an undeniable Indiana Jones charm, and your wry smile and your easy manner make all the robbing and the shooting at least feel OK, if not exactly virtuous.

The game works with Xbox Live, so you can dogfight over the internet with people in Hollywood and Texas and the Industrial States. This is outrageously great fun, and is probably the best thing to hit the network since last year's stompy-robot game MechAssault. You roar into the skies with your guns blazing, hollering 1940s-vintage insults into your microphone, barrel-rolling to dodge incoming fire, and pirates from across the land give as good as they get. It is exhilarating and thrilling and the sort of thing you will have trouble putting down. You will want to go there and stay, see?

All the airships are called "Zeppelins." It is unclear whether the game designers know the word is a trademark and that a German company by that name still makes blimps. Maybe they decided it was more romantic to pretend not to notice.