How hard is 'impossible'?

I played Deus Ex games on highest difficulty. Where do the System Shock games fall into this? Is there a time limit like in System Shock one on "Impossible"?

Does this game react like other Dark Engine games where higher difficulty opens up additional mission objectives and areas, like in Thief 1 & 2?

Is there an option to play for stealth like in Thief and Deus Ex?

"Impossible" is more annoying than hard. You have less HP, CMs cost more and enemies do more damage. There are no additional goals, there is no time limit nor changes in AI behaviour.

It's fun for a one-time challenge, but I like Hard way better, even after ~30 playthroughs.

Pacifist runs are possible (to a limited extent) but a huge pain in the ass as there is no stealth in System Shock 2. Avoid it.

There is stealth in System Shock 2, since it runs on the same core engine as Thief, but the levels aren't set up to take full advantage of it. Nonetheless, you can evade detection by being quiet, staying out of sight, and hiding in the dark. There just aren't many dark places to hide.

Optional challenges are.. well.. self imposed mostly.
Like.. a wrench only run or um.. minimal upgrades/all natural run or something.

I don't think there really is any special bene or slap for doing a self imposed challenge other than the thrill of it.

Harder game modes are just that. Nothing really special outside of maybe how often you die, weapon break/jam, and how much everything costs. entirely possible to theoretically game over by running out of cash and not being able to afford a rez if i recall...

Potential for silent assasination?

Obviously i'm not expecting a pacifist non lethal taken downs in a game about evil cyborgs and insane computers!

I don't particuarly care about ghosting.

You can get the drop on enemies. Not necessarily one hit kill depending on your stuff but it helps to go in before they become aware of you. They don't magically know where you are or whatever, they have some AI if that's what you mean.

I mean more along the lines of taking down enemies without alerting other enemies. Like you can in Thief and in Deus Ex (although in those games its possible to do it non-lethally).

More often than not, you would attract attention. Still, you can quickly finish off an enemy and run away to a part of the map that enemies can't find you - for example, locations that require climbing to pass through or crouching. I have heard that Localized Pyrokinesis and Invisibility is one way to down enemies without the properly noticing you, but never have tried it.

Despite sharing the same engine as Thief, SS2 isn't built for true stealth gameplay - there is no light gem, the levels don't have enough shadows, ect.

If they're not in the same room or immediate area they can be killed without alerting others I believe, within reason.

I'm playing the game for the second time and I'm playing on Impossible; personally, I'm not finding it too hard...

I´m not sure regarding the pacifist run. In one of the later levels you have to collect certain parts, that have been given to several hostile NPC. They won´t give them to you before they are dead.

Most 'pacifist' runs in games that force you to kill something at a point usually ignore the force-kill spot.

Ah, understand I do. Cheap tricks in the discourse they use.

I was about the post a similar question but then I saw this thread.

I'm an experiences player of these types of games as well. I never played Deus Ex but I've played Thief 1,2, and 3 on Expert twice through and SS2 on Normal once many years ago. I'm currently playing through Thief 1 (my 3rd pass through) on expert

My question was would it be an insane idea to play my second run through SS2 as Hard or even Impossible even though it's been years since my last run through SS2?

hard is the way to go, if you aim for the true SS2 experience. impossible is only recommended for the most hardcore players, as you will be dying a lot.