Dues Ex, can it be finished without killing being done? Hmmmm. I didn't experience that. Can't say.
Alright, since it seems you aren't as marked out for DX as I am, I'll explain it to you:
Deus Ex was designed to allow the player to choose their own paths through levels and the game (and I'm referring to gameplay, not story, I'm not claiming the story was open-ended). Yet the way that the designers at Ion Storm intended the game, you had to kill three people in order to continue with the the game: Anna, Gunther, and a guy at Area 51...
HOWEVER, last year, someone succeeded in using Deus Ex's open-ended gameplay design to actually do what the designers intended as impossible: get through the game without harming a single person, including Gunther, Anna, and the guy at Area 51. Even Warren Spector himself had previously said this was impossible.
That is what Systematic Level Design is about. The player creates his/her own solutions to problems the game presents. This is what the physics and design of HL2 allows for.
I know that in Dues Ex 2 they stated that they improved alot on the differnt paths you can take and that 'yes', you can play the whole game stealth and not kill.
In Deus Ex 2, the designers are avoiding making the player kill anyone in order to continue with the game.
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