It goes without saying that Half-Life 2 is quite possibly the best single-player FPS experience ever crafted for the PC. Four years in the making, ground-breaking physics, stunning visuals, non-stop action and a stellar story, to boot all coalesced to create one of the most talked about games in history. Given Valve's penchant to take as long as they need to make everything perfect, it's highly likely any wait for a Half-Life 3 could be just as long and difficult to endure - this is where Half-Life 2: Episode 1 comes in. Rather than make us wait to see what happens between humanity and the Combine in the series' next major installment, the clever folks at Valve crafted a concept to release three expansions tailing the events left at the very end of Half-Life 2. Aptly titled Episode 1, this first in this trilogy has been shaped to take players back to the events that took place at the closing of HL2, only now you get to see (and play) what happens after your devastating actions of that game. Essentially the goal seems to be to tie all the loose ends left hanging after the credits rolled for HL2, and so it's with great vigour I took up the task of reviewing the first true expansion for one of the world's most revered shooters.

First thing's first; if your system can run HL2, it can run the expansion. Nothing has changed on a visual level except maybe a few tweaks and some optimisation. Moreover, if you're familiar with the inner machinations of the HL2 gameplay experience, jumping into this is like riding a bike. With that being said, however, things have changed a little. Some of the puzzles throughout are actually pretty taxing on the old adrenaline, and some of the fire-fights can leave you pretty breathless. Story revelations throughout are also heavy on the noggin, and you have to deal with all of this in the space of between four and five hours of game time. Yep, no kidding.

But it's not all bad. Those four to five hours are going to keep you so glued to your seat, the term "on your toes" has no meaning here (though, for the sake of colouring up this review, the game also "keeps you on your toes"), and while you'll be crying at the end of the whole experience for wanting more and more, Valve does a bang-up job of keeping you excited enough, you'll be happy to wait the six months it's said you will for Episode 2 (sad, I know).

So the expansion picks up directly where HL2 ended. The core explosion in the citadel is frozen in time and Gordon is pulled from the equation, that is, however, until another force comes into play and it appears Freeman's job is far from over and he awakens to the sound of Alyx's voice and pitch black. Soon your pulled from beneath a pile of rubble by dog, and Alyx is elated you're alive, from here she manages to get in contact with her father and it appears the only course of action to get you and Alyx out of ground zero is to go back into the citadel and board one of the outgoing trains. Once inside, things become alarmingly familiar, and even the Gravity Gun (the only weapon you have at this point) gets its stellar boost of power and you can start pulling enemies from vast distances like so many rag-dolls once again.

Inside the citadel, it becomes business as usual, only in bigger short bursts. By this I mean, with the short amount of play time ahead, Valve made the decision to assume you've played through HL2 already and so subtle introductions of enemies, puzzles, weapons and areas are taken away in favour of throwing you directly into the action. This idea does away with a lot of time-wasting movement and level design and keeps the game moving at a fairly consistent pace. Like HL2, your path is pretty well dictated by only one set way, or a few branches that end up at the same point anyway, and in the citadel it's all pretty much set. In here you'll use the Gravity Gun to pull energy orbs to power dead conduits and solve pretty cool puzzles, and for the most part it's a smooth ride making your way through. Once on the train the game's narrative really starts to kick in, as does Gordon's blossoming relationship with Alyx, but be warned, there are some pretty screwed up moments in Episode 1, and they begin on that train.

There aren't any new areas you explore in the game; it's all very familiar territory as you make your way through City 17 in an attempt to evacuate. Instead, what Episode 1 serves to do is set the scene for a new struggle. One of the major elements this game explores and offers is the rebuilding of the human race, repopulating the species, and it's played out fairly heavily throughout. In fact, many revelations like this occur and it seems there was more going on in the background of HL2 than we may have first realised, it helps that throughout almost the entire trek, Alyx is by your side, acting as something of an on-foot narrator to what's going on in the world around you. However, having her by your side can sometimes prove problematic in enclosed areas where you're trying avoid enemies (one new enemy in particular loves to rush at you with grenades in hand, kamikaze style) and her slow to react movement means you'll often get blown up because she didn't get out of your way quick enough. But this doesn't happen all that often, and for the most part she's actually pretty helpful.

I could rave about more here, but given the length of the game's overall experience, I'd end up spoiling it all for you. But just to give you an idea, the whole game takes place on foot (no more driving any vehicles or the like) and most of the puzzles revolve around dropping bridges, overcoming water hazards and reconnecting power conduits. It's all pretty well business as usual, but given the foundations of where this game stems from, that's not at all a bad thing, just make sure you don't come into this expecting some earth-shattering gameplay revolution, because this is an expansion for a reason (save the revolution for Half-Life 3 if it's ever made). It's unfortunate that the game is so short, but believe me when I say it'll be one of the more memorable four to five hours of your life this coming weekend.