If you've never played Half Life 2, you're probably in the majority of the population of planet earth. Admitting as much would result in a shrug.
If you've never played Half Life 2 and you're reading this, you're something of an anomaly. You're in the same boat as anyone who declares an interest in film and then admits that they've never seen The Godfather or Star Wars or any number of cinematic landmarks. Admitting as much is an acknowledgment that you have some required reading to catch up on.
And if you've never played Half Life 2 and you write about video games to make money... well, keep it to yourself.
Admitting as much - as I stupidly have - prompts reactions on a rather extreme scale. "Call yourself a games journalist?", "Wow! Were you in a coma?" and "You're kidding. No, you're actually kidding, right?" are three of the more polite responses I've received from colleagues upon revealing this chink in my armour.
I almost feel like they deserve an explanation. How did this set of circumstances come to pass? I had no money and no PC back in 2004 and I had just met a young woman who would later become my wife, so I was otherwise occupied. I was also quite content in my sub-editing job and if a game wasn't available on PS2, I could happily live without it. In short it was a different time for me in 2004.
Now that I've explained how I didn't get around to playing a video game, let's consider its merits ten years after its original date of release. Well, okay, thirteen years and two months if you're being pedantic.
This is actually harder than you'd think. Unlike a lot of literature, film, television and fine arts, video games do not age well. The best video games maintain their hook on an audience through their ability to provide instant fun all the time. Visuals, soundtracks, level construction and more become antiquated through the passage of time.
The strongest lasting attraction a game has is whether it's immediately enjoyable and accessible. This is why arcade games from the 80s are remembered more vividly than the point and click adventures Sierra used to churn out in the early 90s - and a lot of those were excellent, by the way.
" Unlike a lot of literature and film, video games do not age well."
It's also why a player who is coming to Half Life 2 for the first time ten years after its release might be forgiven for thinking that its first act is rather rubbish. And that its second act is rather boring. And that the first three hours of this game are something of a chore.
I know! Blasphemy, right? But consider this; Half Life 2 begins with an aimless section in which the player ambles about in a run-down city. They are then sent on the run through a repetitive-looking stretch of sewers and then they're tasked with piloting a makeshift jet-ski down a passage of canals. Anyone who has ever played Half Life 2 by this stage will be holding their hands up because they'll remember how terrible the driving sections in this game are.
It may be a product of the last decade in which FPS games became a dominant genre that a shooter without an ironsights mechanic mapped to the left trigger feels off - and Half Life 2 is definitely 'off' in this regard.
This is undoubtedly a product of the fact that this game was originally developed for the PC platform as is the lousy agency players have in platforming sections and Half Life 2's tendency to auto-save at inopportune moments; I counted three instances in which the game auto-reloaded at a point where Mr Freeman was on the receiving end of a killing blow.
Please, if you decide to revisit this game on The Orange Box - as I did - remember that it was originally a PC title, which means you should save well and save often.
Leaving aside the game's PC-centric foibles, Half Life 2 is worth persevering with, even if the first three hours are little off-putting. This is because even when you're slogging through the early stages of Half Life 2, it's impossible not to be affected by the sense that something is decidedly wrong with the world Gordon Freeman inhabits - and not just because it's been overrun by The Combine.
A palpable sense of resigned dread permeates the entire environment from the moment the player steps off the train and into City 17, which feels like what would happen if the Soviet bloc had been constructed in Seattle.
Half Life 2 is inordinately creepy. The most obvious evidence one could use to back up this assertion is the game's superb creature design and its stunning soundtrack, which hasn't aged a day. Headcrabs, Necrotics and Poison Zombies are all as loathsome in both their appearance and their movement as they were back in 2004 and the noises they make - from the high-pitched shrieks of the headcrabs to the anguished screams of a Necrotic on fire -are pitched perfectly on the flesh crawling scale.
"It helps immensely that all of the impressive world building is at the service of a very well designed game."
The skittering, incessant clicking the Antlions make is constantly unsettling it doesn't get any easier to listen to even when the buggers are on your side. I reserve a special hatred for Barnacles; the loping squelsh they make as they reel in prey is horrible and personally, plants that can eat large mammals give me the willies.
The broken world backdrop fills out this ever-present sense of unease. In Half Life 2, the whole world feels sick, in keeping with the plot conceit that the planet is being strip-mined of its resources by The Combine. Other developers might demonstrate this through vistas of demolished housing blocks or stretches of land with craters blasted in them. Valve does it with chipped paintwork, cryptic graffiti, bloodstains on walls and discarded crates and bottles.
The world is presented as a terminally ill patient and this is as true in City 17 with its gleaming citadel looming above pock-marked streets as it is out on Highway 17 with its busted up tarmac and wind howling on the soundtrack.
It helps immensely that all of this impressive world building is at the service of a very well designed game. As stated earlier, if you've been weaned on the twitchy, rapaciously paced shooters of the last few years, Half Life 2's opening three hours, in which the player is encouraged to explore their surroundings as much as they are to gun down enemies, can now feel a little laborious.
Once the menacing synth-lines herald the player's arrival in Ravenholm, however, I found things picked up considerably and not just because of the gravity gun. At Ravenholm, Half Life 2's oppressive atmosphere folds in on the player like a compactor.
It's also here that Half Life 2 starts tossing ideas at the player at a furious rate. It's not like the game was short on variation to begin with, but after three hours set-pieces, puzzles, platform levels and oddities start moving at a clip. Even so, there's never the sense that the player is simply being shunted from one scenario to the next and the rather loose structure helps build a sense of space - even while that space is being packed fat with tension.
Alongside the sections players need to employ their grey matter to solve, Valve mix up the run-and-gun action, throwing turrets, vehicles, tower defence levels, squad-based action and deathtraps at the player.
All of this is complimented by some unique items in Freeman's arsenal; the Gravity Gun's ability to pick up and hurl projectiles and the Pheropod's summoning capabilities are just two delightful curveballs that allow players an open-ended approach to dispatching enemies.
Of course, a lot of what made Half Life 2 so mind blowing when it first arrived in 2004 (I'm told) was the variety it contained as a package. A lot of its level design, mechanics and even stark visual aesthetics have become commonplace in shooters.
Playing Half Life 2 ten years after its release felt like playing through the blueprints for most of the shooter genre on the last gen. It's a bit like hearing Physical Graffiti for the first time if you've ever had a fondness for hard rock and heavy metal.
Like Led Zepplin's seminal double album, Half Life 2 didn't re-invent the wheel for its genre and it's kind of hard to understand its initial impact unless you were present at its release, but I can now see its DNA running through the work of scores of others who have attempted similar creations.
No wonder Half Life 3 is taking so long...