Ezio will be able to swim and dive in the canals of Venice, and we're told that, where Altair could blend with monks, Ezio can blend in with "any kind of group of citizens" in the crowd. You'll be able to move freely while blending too, instead of being forced to walk the same path as your habited friends. While weapons such as warhammers and axes can be snatched from guards, unarmed combat has been made more complex and involving to encompass a wider range of combos and to that effect, there's a spate of new assassination moves too.
We doubt Ezio will get a jump button (and whether we'd want him to is questionable), but other game elements are definitely being tweaked. Buildings can now be entered and explored, a feature which only barely appeared in the form the original's safe houses. The mission structure of the first game was rigid and repetitive; a routine of finding your agent before climbing to the tops of towers to discover three different kinds of investigation events on your map.
This time around, those types (eavesdropping, interrogation and pickpocketing) have been extended to 16 (a number Ubisoft say could rise). And rather than successful events simply accumulating until you reach a point where you can move to your primary assassination target, missions will branch and diverge, unlocking new agents and unique missions. What those 16+ mission types will involve isn't yet known, though they'll go a long way towards dissolving the tedium felt during the first game.
There's more. Optional missions will be spread throughout the cities of Venice and Florence, on which listless assassins might be tempted to spend their time. If you've gutted your screaming target in a busy town square and don't want witnesses saying what a rubbish assassin you are, you can hunt them down and silence them (ideally in a subtler manner).
Your crimes will be noted too - every action you take will be tied to the game's notoriety system, in which you gain a wanted level in each city you frequent. Presumably there are consequences of becoming the most wanted man in Florence, benefits of being the most feared man in Venice, and ways to get the authorities off your case with bribes.
Other agents will crop up alongside Leo, including Botticelli, the powerful Medici family, and Machiavelli, a man so scheming he has his own adjective and an assassin's guild loyalty card. Around these, two major factions will operate in 15th century Italy: the Thieves Guild of Venice - purported to be the beginnings of the Mafia, and conduct themselves as such - and the Courtesans of Florence - high-class hookers (see Faction Stations).
Assassin's Creed II will be more than a simple scenery swap then, taking key features from Altair's adventure and expanding on them while introducing new ideas. Most exciting is the fact Ubisoft have sorted out the botched mission structure. The one-dimensional progression of the original was the biggest sticking point for many, so tying missions to characters and allowing their outcomes to lead to other missions makes a very big sack of sense.
We'll have to see how wackiness such as Da Vinci's flying machine fits into this new equation (apparently we'll be able to carry out assassinations from the thing), and beyond Venice, Florence and the surrounding Tuscan countryside, the locations Ezio will visit haven't been confirmed. There's also an economy system yet to be unveiled, which will no doubt see Ezio paid with cash that can then be used to buy Da Vinci's wares.
The first Assassin's Creed was a deeply satisfying game to play, one whose lack of substance was obscured by the thickly laid on style - a sequel that injects worth into the original's hollow shell of spectacle would be something very special indeed. Assassin's Creed II might have avoided the stench of Venetian reality, but it's also steering well clear of the stink of... um... not learning from mistakes.