I feel bad for those few people out there who get motion sickness when they're playing video games. Very bad indeed. What a shame, I think, that for some this fantastic hobby is ruined by nausea. I count myself lucky that it never happens to me, but then I remember that there's an exception to that rule: the Thief games. Both Thief 1 and 2 used to make me feel very, very ill after extended periods of play, and I didn't help myself by extending those periods almost to the point of being physically sick.

I'm serious. I couldn't tear myself away from them, from pushing my way through that thick, inky darkness, edging down corridors and squeezing my way into corners, even as my stomach seemed to swirl and twist inside me. I don't know why my body rebelled so. It wasn't the fear and it wasn't the tension. Maybe it was something about that dense, heavy blackness that coated these games, that bled into every texture, that made them so grim and so dour.

Or maybe it was simply the game world itself, often harsh, cruel and deeply unpleasant. The picture painted by the first Thief was of a cold and unsympathetic city and its sequel built upon those ideas, drawing out the finer details of the heartless, unfeeling religion that sat at its core. In Thief 2, that already severe religion would experience a terrifying extremism as, of course, would you, the player.

That's way too many guards. This is not a safe place to be.

This wasn't a sequel about pushing technical boundaries or taking the series in a different direction, as it was functionally and recognisably the same as Thief. Instead, it represented a tightening of focus and, much as it added greater detail to its game world, it also placed a greater emphasis on everything that Thief was really supposed to be about: hiding, sneaking, a sense of terror, a feeling of being almost powerless. Thief 2 brought players a meaner world and a harder game.

First, a little about that meaner world: the stoic and unfeeling religion at the core of Thief was the technocratic Hammerites. Immutable and almost emotionless, their chilly cathedrals were constructed in tribute to the Master Builder, whose example as a creator and inventor they strove to follow through a prohibitive and punishing codex. Joining their ranks in this sequel was the mechanist Father Karras, an inventor so enamoured with technology that he eventually broke with the all-too-human order to begin building his own collection of biomechanical, steampunk followers with which he would eliminate all of the city's organic, imperfect life.

This gave Looking Glass the chance to introduce a multitude of mechanical monsters, creatures that you couldn't deal with as you would have Thief's guards and militia. Great bulbous robots, their sensors all too capable of picking up the sound of your footsteps, couldn't be blackjacked and dragged into linen cupboards, while all-seeing sentries launched bombs your way. Your enemies were tougher because, as was always the case, the point was to avoid them, not to face them, while many of the levels were trickier, tighter and gave you much greater opportunities to embarrass yourself by being seen or heard. You might've got by swinging your sword a few times in the first game, but now you really had to think like a thief.

Looking Glass also added much more colour to the world that they had sketched out in their previous game, providing larger and more urban levels set in banks, temples, police stations and even out in the streets of the city, as well as sending players into a haunted library or tasking them to board a steampunk submarine. Once again, all these were littered with letters that helped bring both the levels and the world to life, often through a series of gentle, subtle hints rather than any direct exposition.

And, of course, there were more of those absolutely gorgeous cutscenes. The Thief series still boasts the very best cutscenes in all of gaming, a beautiful mix of live-action actors and hand-drawn animation quite unlike anything ever seen since. Those are almost my favourite things about the Thief games. Or perhaps they're my favourite things on odd-numbered days of the week, because there was something else that the series did a frankly astonishing job with, something that Thief 2 also took the opportunity to build upon, and that was glorious, glorious sound. Not only were the Thief games busy caring about the amount of noise that you made, they also kept themselves occupied making a plethora of peculiar noises of their own, more than a few of which were downright scary. Perhaps it was these that caused me to feel unwell.

On top of the original's babbling Apparitions and cackling Haunts, the sequel's clockwork constructs muttered and mumbled to themselves as they stomped their way about the levels. Machinery thunked, lights hummed and footsteps clacked upon metal. Karras himself was a disturbing character to hear, perched on the precipice of madness, and it's almost incredible to believe that he was voiced by the same gravelly-voiced actor who also played the titular thief, Garrett. Karras' best moment is undoubtedly spread across half a dozen recorded messages that he leaves for his dinner guests to listen to in his stead, across which he desperately tries to mask his almost childlike excitement at what he has planned.

Even now, the Thief games still stand out for their sound design, one of the series' greatest strengths. While their graphics may seem borderline prehistoric now, our ears don't make the same demands that our eyes do and Thief 2 is still able to make use of that direct line straight into our brains, remaining an auditory treat twelve years after release.

Still, as you may be aware, recent and rather unexpected patches were released for both Thief 2 and System Shock 2, over on the Through The Looking Glass forums, which will give both games something of a lick of paint.

I have to admit, I haven't tried it yet myself. I know that's because, should I step back into that darkness once again, I'll once again be swimming my way through it to the point of illness, using every ounce of my will to tell myself that I can play for just five more minutes, regardless of all the time it's already stolen.