The biggest change to the game play is that it uses a new engine that is a lot less troublesome with modern computers. The new and improved graphics are not just for show, all shadows are now fully rendered and move like normal lights, putting a grater focus on shadow base game play that it's predecessors were built from. Guards AI had been improved and now can notice loot that has gone missing. The only negative side to the improvements is that the missions now are divided up viva long loading screens. Features like swimming were removed and the ropevine arrow has been replaced by climbing gloves. I am leaving out the story because I don't want to spoil it but Thief Deadly Shadows is the same Thief game that everyone loves and knows but now even better.
