There were a lot of really interesting decisions that went into planning how the A.I. in Thief: Deadly Shadows were going to respond and interact with their environment. We knew early on that we were going to be writing the A.I. code from scratch, so we had an opportunity to think about the core stealth experience in Thief 1 and Thief 2, what was wrong with it, and how we could improve upon it. Thief: DS required a lot of unique features -- not present in Thief 1 and 2 -- in order to fulfill the vision of the game: non-hostile A.I., a faster and more advanced combat system, factional relationships, etc. However, our ultimate focus rested on the core stealth experience. The biggest questions on our minds were, firstly, how we could maintain stealth tension while retaining an action feel? And secondly, how we could improve A.I. spatial awareness of their surroundings during searching?

So, right away it was down to business. We spent a bunch of time looking at stealth games on the market, and, of course, analyzing Thief 1 and 2. Actually, we spent a lot of time playing other stealth games … definitely the hard part of the research!