What do you get if you take Half Life, revamp the graphics, add vehicles and a more grand, cinematic storyline, and mix in some Big Brother and War of the Worlds ambience? We'll give you a clue - it begins with H and ends in a 2. And it's not Halo 2. Or two thirds of a water molecule.

Half Life 2 begins where the original left off in many ways. As Gordon Freeman ("I am not a number...", etc.) you regain consciousness in a train carriage haunted by visions of the enigmatic G-man. The locomotive soon comes to a halt and you're dumped out into the station of a city in the firm grip of 1984, with large screens broadcasting the dictator's messages, shock troopers stun-prodding everyone and strange robots flying up into your face, taking photos with a blinding flash.

Reviewers always bang on about the atmosphere of a game, but Half Life 2 deserves special mention in this rather cliché-ridden department. This initial section feels intrusive and intimidating, setting the scene perfectly. Of course, the fact that the game looks fantastic helps carve out the realism, with fabulously detailed locales (especially the vast outdoor scenes) and facial animations on the characters which will blow you away (they're eerily expressive).

Rather like Doom 3, Half Life 2 carries a great deal over from the first outing including many of the same weapons, monsters, even the sound effects. However, where Doom 3 also brought with it the baggage of the original's linearity (get the red key, open the red door, look for the blue key...), Half Life 2 manages to deftly side-step this issue with a much more liberated feel.

The deft, clever bit is that in reality it is a pretty linear, channelled shooter, it's just that the level design camouflages this admirably. It doesn't have that Doom 3 "now get this key" vibe, rather there's a series of long sprawling levels which burst with a variety of events including skirmishes, heavy battles, vehicle sections, puzzle bits and just plain cool stuff.

Examples? Skip this paragraph if you're not keen on spoilers... for those still reading, in the buggy driving level you've got to bridge a chasm by dextrously manoeuvring a huge shipping crate into place using a crane. Another level set in a prison requires you to set up automatic machine guns to deal with incoming waves of enemy troopers.

There's a great deal of variance in what you're doing and this makes Half Life 2 an absolute joy to play through - plus everything is neatly tied together with an excellent overarching storyline.

Is Half Life 2 faultless? Very nearly. We encountered a few AI glitches, such as a soldier just standing there while we shot him and a couple of stuck monsters. Then there's the rather overbearing music which needs turning down in relation to the sound effects, and the high detail visual settings which require a good PC spec. The odd indoors section can look a little samey, but this is a rare occurrence and all of these criticisms do nothing to detract from the fact that Half Life 2 is a simply stunning single player experience.

On the multiplayer front you get Counter-Strike Source, the graphically superior version of the classic team and objective based deathmatch which pits terrorists against counter terrorists. This is as good as ever, although it seems a little odd that there isn't actually a vanilla deathmatch mode using Half Life 2 itself.

Of this year's two big shooters, Half Life 2 takes the crown over and above Doom 3. The latter was impressive, but this is an outright classic and an absolute must purchase for any FPS fan.