Playing the new Xbox 360 demo for Assassin's Creed at this year's E3, I finally got a feel for what makes the game so mesmerizing: its beautiful fluidity. The effortless flow of the protagonist's movements permeate the gameplay as he essentially swims through a sea of bodies and buildings. Just running on rooftops and climbing on walls without having a mission is a great deal of fun, which says lots about the game's playability. This element actually reminded me of Real Time Worlds' Crackdown in an exploratory sense, though jumping through the cities in that game lacked the elegance of Assassin's hero.