And in 3D open-space games such as H&D2, Far Cry etc,
a whole lot to do with AI as well. Replaying a level with
scripted AI, and knowing exactly where the enemy will
appear and how they will react gives zero re-play value.

Playing Vietcong I'm continually astounded in the variety of AI
placement and behavior that this game offers. For instance I'm now trying
to complete one of the quickfights (Arroyo). It's quite difficult, and I've
restarted the level literally dozens of times, and each time the initial AI
placement and behavior is slightly different. Very impressive.

rms