Artificial Intelligence
One of the major challenges in developing a good first person shooter is crafting believable opponent behavior. As challenging as this is with standard shooters, it is that much more complicated when you throw time control into the mix. How should an opponent react, for example, if you walk right past him while time is frozen? How should he react if he sees you and then you reverse time and hide?
The answers are clear: if time is stopped for an opponent, then he should not notice you at all. And if you take it further and steal his weapon during time stop he should act bewildered. If time is reversed, then AI states should reverse as well. An opponent who has just noticed you can be reversed back to blissful ignorance. These are not simple things that just "happen" - they all have to be hard-wired into the AI code so that opponents act naturally and as expected in such situations. In addition, special animations have to be created and voiceovers must be recorded that accompany such behavior.
From a gameplay perspective, you can really see how the use of time powers and its interaction with AI can create some cool opportunities for gameplay. Imagine, for example that you are severely outgunned. Why not stop time and sneak past some heavily guarded opponents? What if you walk right into a trap of hidden opponents? Why not reverse time after they have pounced on you and get out of that trap and strategize a better way around the obstacle? The use of the time powers and their interaction with the AI allow each player to approach a challenge differently. This is one of the really cool aspects of the actual gunplay and one that makes the game much less of a linear experience.
