This is easily one of my top five favourite games of all time. It may be my favourite. Simply put, it is a pure stealth game. This is a game where, if you get into combat, you're pretty well screwed (and on the highest difficulty, you are actually not allowed to kill anyone human, though you can knock them out). Everything is about careful planning and good execution. The levels are about as nonlinear as I have ever seen in a game, and the challenges often have multiple solutions. After all this time I would still say this game is phenomenal. For an extra challenge, try to play the hardest difficulty without even knocking anyone unconscious (the 'Lydia style' of play, named for a famous Thief player). The only problem with this game is, after playing it, almost no other stealth game will feel worth looking at.
