The crowd stops short of being an obstacle, too. After a few minutes you're happily weaving through and around the people at surprising pace, using your "gentle push" button to brush through without causing a ruckus, or dodging them completely by climbing, jumping or just, you know, not running directly into them. Much as you would navigate a crowd in real life.
Occasionally you do alert the guards though - whether by knocking people over or doing something suspicious within their line of sight, or by attacking them, for that matter - and so they give chase. And fight. And here the game looks even better, as Altair stands poised with his sword waiting to strike.
It's a perfect blend of combat mechanics and animation. Swords clash and clang against one another, and guards grab you and try to throw you to the ground, but you twist their arm and boot them away. Physical contact is near perfect. Your hand wraps around their wrist, they buckle in pain as you rotate them away from you, and your foot makes solid contact with their backside as you boot them into a wall. And when they attempt to tackle you, one by one, you counter devastatingly. The execution of these counters - unlocked early in the game - is similar to the good old Mark of Kri. Remember that? Probably not, but I like to reference it.
Locked on to any opponent in a crowd, you hold the block button and wait for them to strike one by one, and as someone advances you hit the counter button and Altair deftly avoids their blow and savagely brutalises them in response. Whether it's driving his sword upward through their chest, striking at their calf and then spinning into a downward stab through the heart, or breaking their sword arm with the flat of the blade and then slicing them nearly in half, it's amazingly brutal (especially for a 15 certificate - watch out, Mum).
There is a system of parries and attacks to master for those of you with a passion for fighting (although it's hardly Ninja Gaiden), but being able to shortcut the entire combat system with satisfying counters demonstrates a tacit understanding of the division between gamers who enjoy third-person combat and those who just want to get it out of the way.
Within a couple of hours, then, a structure emerges: receive your target, gather intelligence and then strike. Again, a bit like Crackdown. In fact, the parallels are increasingly uncanny. Granted, Real Time Worlds' Xbox 360 game had guns rather than swords, and it preferred speed, height and regular platforming limitations to the subtlety of Altair's urban mountaineering, but the comparison certainly stands up for the most part. Except, while you could lessen the strength of your enemy's force by taking down his lieutenants in Crackdown, Assassin's Creed is more regimented: you must complete a number of investigations before striking at the target.
And these, frankly, become a bit dull. Eavesdropping involves sitting on a bench, locating the source of the gossip, targeting them and pressing Y. That's it. Pick-pocketing involves much the same, except you have to follow someone for a bit and press B when your hand's within grabbing distance of their back pocket. It's sleuthy, but also a bit one-dimensional. If you get spotted, you hide until the heat's off, then go back and try again. The same's true of interrogations - listen to some chatter, follow them for a few seconds, then punch them until you get a cut-scene. That's not simplification on our part; that's literally what you do.
Each section of each city is also home to around a dozen innocent strangers - scholars, monks, damsels - who are being slapped around by the guards and need to be liberated. These encounters are identical to one another: start a fight, kill all the guards and then target the rescued civilian to receive praise and - as reward - the loyalty of some nearby vigilantes, who will block the path of guards if they ever pursue you through the same area.
The informer missions are no more varied, but are more fun to do. Generally they involve stealth-assassinating a few targets (later in the game, time limits are imposed), which is a careful task of finding them on your mini-map, walking up to them, quietly stabbing them with your concealed blade, and then beating an inconspicuous path to the next target. Doing these without alerting the guards is the closest the game comes to making you feel like a proper assassin.