We all know that Duke Nukem Forever has been in been in development for 13 years. The fact the game is going to see the light of day at all is a testament to the wills of the nine 3D Realms staff who kept working on it in secret after their employer's demise, and to the artistic sympathy of Randy Pitchford, president of Gearbox Software and one of the industry's great showmen.
But the craziest thing about Duke Nukem Forever's "development hell", as Pitchford refers to it, is that the game's age has become its unique selling point.
And make no mistake, this is a 13-year-old game. The developers have slapped some lipstick on the odd pig but the occasional modern graphical effect - like depth-of-field as you change your focus between an armoured snout in the foreground and an assault trooper further away - jars with lighting arrangements, boxy geometry, angular character models and textural detail that often lacks the definition and subtlety we came to expect after Half-Life 2 in 2004. You never feel as close to 2011 as you do to 1997, and despite the ageing technology the frame-rate of the Xbox 360 version I'm getting to spend 90 minutes playing is inconsistent.
Duke's sense of humour remains just as unreconstructed as the visuals are of their time, complete with cultural references that the kids of today won't understand ("I'm from Las Vegas and I say kill 'em all!" Five points if you correctly identified Starship Troopers), while his menagerie of alien opponents do things that the rest of the FPS genre gave up on years ago.
Assault troopers hover through the air, dodging left and right or teleporting across the screen with frustrating unpredictability. The newest trick the basic pig enemy has learned is to launch himself toward you using muscular hind legs, so that he crashes wavelike against your fumbling macho hands with the geometric precision and violence of the Fiend from Quake 1.
(Which means that, yes, they've borrowed a trick from an enemy in a game released six months after Duke Nukem 3D, and so long forgotten that even its second sequel is now a budget release available via digital download services and as a free-to-play PC browser game.)
As we noted during last year's improbable public unveiling, Forever begins with Duke being blown by the "Holsom Twins" while he plays his own game on a big-screen TV in the penthouse of his casino, The Lady-Killer.
This is where he's spent the years since he last repelled an alien invasion, living the kind of energetically hedonistic lifestyle that sounds really amazing when you're watching it in a buddy comedy, but which most of us would probably rather avoid in favour of a night in with a DVD of Starship Troopers and a takeaway.
Outside the window an alien mothership hangs over Las Vegas. The aliens arrived a little while ago, claiming to have come in peace. The President has asked Duke not to get involved while delicate negotiations are taking place.
So instead, Duke descends in his golden elevator - adorned with framed magazine covers showing him chomping on cigars, cradling pistols and sharing his unself-consciously one-dimensional thoughts on "babes" - to appear on "Damn, It's Late", a talkshow that seems to be filmed in his basement.
But! As he arrives on set, news breaks that aliens are out on the Strip at a Duke-themed burger joint and the blanket coverage from TV stations has forced the show to be cancelled. (Confused younger readers may wish to Google "We interrupt this programme" in order to understand what happened in these situations prior to BBC News 24 and Kay Burley's helicopter.) The game instructs you to divert to the "Duke Cave" for a briefing with the President and General Graves, commander of the Earth Defence Forces.
As expected, the aliens drop their peaceful pretence and come looking for Duke. At this stage he has to fend them off with his bare fists, and the game uses the slow start to introduce mechanics - such as the concept that consuming beer "makes you stronger".
(When I do this, the screen goes so blurry that it's impossible to fight and I can't work out if my strength has actually increased. But I suspect it has, because in a game where you can enhance your health by punching a "douchebag" in the face, it's hard to imagine any of the events that occur are cautionary rather than literal.)
You can also scoff steroids to make yourself go berserk, and at some point the lights go out, so it's time to use "Duke Vision" to see in the dark and take out aliens as they flail uncertainly into the gloom.
In Duke's nearby gym you can boost your health by bench-pressing a pile of weights, throwing a basketball through a hoop (assuming you can decipher the peculiar physics) and playing pinball. A pattern is established at this point: move through an area by killing all the aliens, probe the margins for secret bonuses and jokes (like glimpsing a pair of naked women through an air-vent, writhing and luxuriating on a bedspread), and solve the occasional puzzle.
The puzzles are welcome. As Duke tries to power up his casino so he can take on the mothership, a sexy female computer voice tells him he has to locate three power cores. Two are lying nearby, but the third is on the other side of bulletproof glass in a room full of crates and a toy monster truck.
Seizing the remote control for the truck, Duke has to manoeuvre it up some ramps and around shelving units to dislodge the power core and poke it through a hole in the floor for retrieval. "You sure know how to turn a girl on," purrs the computer, as he inserts the final core.
With the old lady up and running and the mothership waiting outside, it's time for a bit of girl-on-girl. Duke hops in a turret and rides up to the roof, where he proceeds to blast the alien ship with endless rounds while it fires a cannon at him and spits out dropships.
They prove no match. "Rest in pieces," Duke offers as the alien saucer disintegrates and ploughs into the Vegas skyline. (That "girl-on-girl" thing was my joke, by the way - I'm trying to get into the spirit of things.)
As he works his way back down through the casino, Duke is reduced to a tiny, helium-voiced Duke Shrunkem. Apparently his impact on the ladies is undiminished, however - "I know just where I'd put him," a young woman remarks as he passes.
Duke then encounters a child (who fortunately does not automatically want to have sex with him), from whom he borrows a toy car that he drives around the crumbling casino, jumping gaps and revving past oblivious alien swine.
At one point he has to hop out and negotiate stacks of chips, bouncy cushions (SiN! Lest we forget!) and roulette tables ("Always bet on Duke...") to get to the release switch for a metal shutter door.
Having reached safety and a particle device that returns him to his normal stature, aliens descend through the glass ceiling and - following a hairy encounter and the expenditure of a lot of shotgun shells - make off with the Holsom Twins.
Duke, as you can imagine, is incensed. "Not my babes! Not in my town!" He fights his way back through the casino (giving you a normal-sized take on the sections he ravaged in his toy car) and rendezvouses with Graves, who tells him the aliens are heading for the Hoover dam. "Screw the dam. Where are they taking our chicks?"
The EDF forces furnish Duke with a Ripper (the three-barrelled machinegun from Duke Nukem 3D) and some power armour ("Power armour is for pussies," Duke explains as he walks past the Master Chief's unmistakeable green and black helmet).
From here it's a battle through streets heaped with abandoned cars and buses (abandoned, perhaps, due to their low detail levels) and onto a showdown with the Battlelord - a three-storey armoured Rancor impersonator with a machinegun and a mortar cannon.
Having decimated its health bar with RPGs, Duke finishes the Battlelord by ripping a spike out of its head and shoving it through its eye, before dropping to the ground and speed-bagging the monster's testicles for a final humiliation. Fade to black.
Before we sit down with the game, Randy Pitchford tells us that it's nearly finished, but that around 3500 issues are still lurking in the database waiting to be solved. Unless one of them is "overhaul graphics engine", I'm afraid none of them is going to make Duke Nukem Forever feel like a modern videogame.
(It is worth noting that when I speak to him afterwards, Pitchford is incensed when I say I think the game looks outdated, and makes a good defence of its visuals and the trade-offs the studio has made to ensure the experience delivers what 3D Realms intended. Look out for that interview soon for more.)
It's also possible that the playable demo promised to buyers of the Borderlands Game of the Year Edition will backfire, as it reveals to uneducated gamers curious about this impossibly long-awaited first-person shooter that the impossibly long wait has been for something sired by and locked into a 13-year-old design mentality.
Duke Nukem Forever's release will not be a Half-Life 2 moment - when the majesty of Valve's creation suddenly justified the endless delays and broken promises. But while it is old fashioned, unashamedly brash and ridiculous, and full of comically daft one-liners, it also emerges at a convenient time: as an entire genre of unwitting dinosaurs stomps around in gigantic footsteps left by Call of Duty and Halo, Duke's lewd, unapologetic one-dimensionality and lowbrow thrills are points of distinction.
You may laugh uncomfortably at the borderline sexism, and you may log onto a forum occasionally to make fun of the graphics, but the ageing ideas and references that date the game also give it a sense of history and belonging.
And when your morbid curiosity about this 13-year-old game eventually dissipates, the chances are you will look back on the experience with amusement and a certain amount of affection. And if not? It is safe to say the Duke will not lose sleep - although whether he will be back is another story.