Bungie sees ODST as somewhat of a departure from its previous Halo games. Which is true - the main campaign gives players control of an ODST in an open-world environment and the ability to play levels in any order you like.
But you know from the second you throw your first grenade and melee your first face that this is still good old Halo, through and through.
As huge fans of the series we feel a sense of relief that ODST, which was rumoured to be an all-out stealth game, doesn't mess about too much with the tried and tested formula. However, there are some significant differences from Master Chief's outings.
To start with, considering they're supposedly inferior in strength and agility, playing as a lowly ODST brings with it plenty of changes. Bungie says that the human troopers move more slowly and don't jump as high as the super-powered Spartans, but to be honest we didn't really notice in our hands-on time.
What we did notice though is the increased damage taken from long falls, melee attacks and explosions that actually shunt you off your feet. You've got no shield either, and no radar tech on your suit.
This time around you're forced to make do with a health bar that doesn't recharge unless you collect health packs. But this actually makes less of a difference than Bungie makes out, because in place of your old shield is "stamina".
Like Call of Duty 4, when you get shot the screen goes a shade of red, but this doesn't take away health. When the screen reaches its deepest red, bullets begin chipping away at your health bar so you have to hide for a few seconds and allow normal colour to return. It's like having a shield anyway, but with a health bar too - basically like Halo 1.
Bigger differences are evident when you leap into the main campaign. The opening scene, which reveals just how much the Halo graphics engine has improved, shows you tooling up for a mission infiltrating a Covenant ship. Only the ship makes a jump into space, wrecks the city below and sends you slamming into the ground.
Waking from unconsciousness six hours later, your team is missing, the city is deserted except for roaming Covenant patrols, and you're left to uncover the mystery of exactly what happened in the city alone. This forms the hub world from which you will gain access to other levels in the game.
It's like nothing in any previous Halo; dark and eerie with a calm but moody background tune setting the tone. It's an absolutely enormous open world - larger than any level in any other Halo game, Bungie tells us. And you can go wherever you want.
Or at least you will be able to. At first, most of the city is closed off, and you use your new visor - which amplifies light and outlines enemies and objects of significance - to locate a ringing payphone. Interact with that and you get information from a city-controlling AI called the Superintendent.
The Superintendent, which would usually control the street lights and other mundane tasks says Bungie, gives you a map and waypoint markers to areas in the city where a significant event has taken place. This is the structure of the game; you fight your way to a waypoint marker, locate a significant item there and this triggers a flashback of what happened earlier.
You play these flashbacks, which form the games individual missions, as the ODSTs. Bungie only showed us the level on the bridge that was shown at E3, but by the looks of it these missions are more like your traditional Halo levels, with a set path and mission objectives.