As far as the rest of the cast is concerned, things remain mostly unchanged from the last outing. Certain old friends make a welcome return (but we won't spoil that particular surprise), both for cameos and for longer stints, and the roster of evil cannon fodder is all intact, with the only notable addition of Combine Zombies - or 'Zombines', as Alyx offers up, somewhat bemusedly, upon first encountering one. Combine soldiers that have succumbed to a snog from a Headcrab, the Zombines, as you may expect, make for the toughest opposition for the course of Ep1, and especially so when they come piggybacking a few poisonous black Headcrabs, at which point 'legging it' should definitely be residing amongst the favourable new entries of your 'to do' list.
Also new in terms of the native flora and fauna is the fact that City 17's iniquitous inhabitants all seem to have gone for a bit of a wander. Rather than each area you encounter playing host to either one or the other, you can now find yourself up against the likes of Combine forces, Zombies, Headcrabs and Man Hacks all at the same time in a particular battle. While this can make for even more intense and nerve-racking shoot-outs, there's also the added bonus of the fact that these chaps are not particularly keen on each other either, and will therefore regularly fight it out between themselves, oblivious to your presence, as you sadistically sit back and take in the view.
A prime example of such fun has to be watching the Antlions clear your path of Combine soldiers from the safety of a neighbouring street corner. And while we're on the subject of Antlions: they are not - we repeat NOT - your friends anymore. Despite all the good times you may have had together, running up to the first Antlion you see and trying to give a big "boy I've missed you" kiss is not a good idea. And to make things even more difficult, the big floor-thumping devices that previously provided what little safe haven there was from their infernal re-spawning are nowhere to be seen, leaving you in need of alternative solutions to your spiralling arthropod population problem.
Weaponry is never in short supply, however, with the full unadulterated arsenal making a welcome return, not to mention the indispensable Gravity Gun and that ever-iconic crowbar, the former of which serves as your only form of defence for the entire duration of the first chapter. Still no sign of the elusive blue-lasered sniper rifle though - note to self: add that to the list on the Jim'll Fix It style begging letter we're currently drafting up for Gabe Newell.
Now it will probably seem to most people - especially the ardent HL2 devotees out there - that the majority of the above contributes to the conclusion that Episode One is essentially more of the same, and therefore nothing remarkable to shout home about. Subsequently, it's highly probable that some (this reviewer included, initially at least) may experience just a slight twinge of disappointment when faced with the realisation that a brand new adventure is not on the cards. However, in all honesty, this would be to fundamentally miss the point. Episode One never promised anything but the immediate and faithful continuation of one of the greatest games ever made - a loving comfort to the cries of woe that ricocheted across the gaming populace the very second HL2 came to an end.
And for this it cannot and should not be faulted, and Valve can only be commended, as it has essentially achieved everything it set out to do in grandiose style. If anything, the game is just not long enough, and your four (to six) hours seem to be over at what feels like only halfway through the crescendo. But all good things must come to an end and, thankfully, an encore is only a mere six months away. Perhaps this next instalment will be longer; perhaps it will take us to uncharted territory; and perhaps it will finally let us get our dirty mitts on that flipping sniper rifle. But at worst, perhaps it will merely be another four (to six) hours exactly like this one, and if that's the case, we can't wait.