By Mark Ward
Technology correspondent, BBC News website
It might seem odd to review Half-Life six years after it first appeared, but the furore surrounding the imminent release of sequel made me wonder if the original justified such fevered expectations.
Alien enemies work together to catch you out
The only way to do that was to re-install it and play it again.
And what surprised me the most was how well it still compares to games from 2004. It was still very enjoyable to play through even though, it must be admitted, it looks rubbish.
The biggest difference between then and now is in the graphics, especially compared to games such as Doom 3.
Though Half-Life is ahead of that game as, unlike Doom 3, it lets you use a torch and gun together.
Close-up the scenery in Half-Life dissolves into chunky pixels and the people inhabiting the place look like they have been hewn by a poor sculptor.
But the other surprising fact is how you only notice this every now and again. The playability is still apparent and helps to compensate most of the time.
Seeing the opening scenes again, in which Gordon Freeman takes a train ride through the Black Mesa Research Facility, brought back memories of the thrill I got first time I played.
I remember being impressed that I could move around the train carriage and take a closer look at some of the things that it was passing.
It gave a sense of being involved from the start, something that is lacking in many games. Now you just get a cinematic game intro in which you are an observer, only after the impressive opening scenes are over do you join in.
In the original Half-Life this sense of involvement grows when you step off the train and people start talking to you, mentioning that someone is looking for you and that you are expected in the test chamber.
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Once the horrors are unleashed and Gordon has to fight his way to freedom, Half-Life also shows how far ahead of its time it was.
This is largely because the monsters and soldiers that are Gordon's enemies are not one-dimensional, scripted entities that only activate if certain conditions are met.
Instead while playing I regularly came across firefights between soldiers and alien slaves that started before I got there. That is something that would not happen if they were just animated scenery and, to be honest, does not happen enough in many modern games.
All too often in a game you can stroll right up behind a monster or other enemy and kill them without them even spotting you. That seems to rarely be the case in Half-Life.
In particular, I despise headcrabs for their ability to catch me out, time and time again.
The monsters know about their surroundings and will ambush you or work together to flush you out.
The soldiers too were also fiendishly difficult to kill as they used flanking manoeuvres and every weapon they possessed to try to take down me in the guise of Gordon.
The other surprise was how much better at Half-Life I was this time.
I have played a lot of shooters in the last few years and, I guess, so has everyone else which made me realise how much higher the bar has been raised since Half-Life came out.
Half-Life 2 is more realistic
But even I was gratified at how straightforward many parts of Half-Life were this time round, especially the bits that demand you make Gordon jump with pinpoint precision.
I blush to recall how many times I had to do some of the jumping sections, such as the leap across the lift shaft to the ladder on the far side, when I first played.
One of the criticisms you can level at Half-Life is that it does rely a little too much on your ability to make Gordon jump from place to place.
But it is not really much of a criticism when you take into account the size of the Black Mesa complex, the different environments Half-Life is spread across, the intelligence of the enemies and the thought that went in to putting it all together.
In 1998 when Half-Life was first released it stood out in a year that also saw the launch of Starcraft, Grand Theft Auto, Baldur's Gate and Thief.
Half-Life 2 has a lot to live up to.