The game's greatest design flaw may be that it's a bit too open-ended for its own good, refusing to overtly reward or punish players for behaving in a specific way. If you wish, you can spend a lovely afternoon playing Maniacal Guard Killer's Creed instead, carrying out your missions with all the stealthy maneuvering of a grand piano rolling down an escalator. Would it have been wiser for Ubisoft to beat you over the head every time you set off a medieval alarm and otherwise played the game "wrong?" Perhaps... but isn't the point of open-ended gameplay to let you choose your own path?
In many ways, Assassin's Creed is more of a role-playing game than most of the titles officially labeling themselves as such. When you play as Altair -- really play as him, as an assassin -- and measure failure according to your own actions and not what a Fission Mailed screen tells you, the game's intricate world becomes inescapably engaging. Learn about your target, plan your attack and revel in the absolutely thrilling chase that follows your murderous deed. Though the game's overall structure may seem repetitive in the face of such a believable world, the true magic in Assassin's Creed lies not in what you do, but how you do it.