Producer Alex Cutting teaches Daniel Emery how to take on a new player role in Halo 3: ODST.
Microsoft has shown off the full version of the long-awaited follow-up to the first person shooter, Halo 3, ahead of its launch on Tuesday.
The Halo series is one of the most popular video games of all time, selling millions of units worldwide.
Set prior to events in the last game, Halo 3: ODST allows gamers to take control of an elite human soldier fighting hordes of alien invaders.
Halo 3: ODST will be in the shops on global release 22 September.
Initially developed as a add-on to fill the gap between the big instalments of the game, it snowballed into a stand-alone game in its own right.
Piers Harding-Rolls - senior analyst with Screen Digest - told BBC News that the title was "very big" for publisher Microsoft and that previous versions had done "fantastically well".
"We expect it to sell well and the OTX data - which looks at what gamers intend to purchase - has Halo 3: ODST top of the list," he said.
"The last version - Halo 3 - sold more than eight million copies worldwide, although it is difficult to say whether it will be as big as the last one," he added.
Set toward the end of this millennium, Halo 3: ODST - which stands for Orbital Drop Shock Troopers - sees the human race engaged in a life-or-death struggle with a coalition of alien races called The Covenant.
Speaking to BBC News, Alex Cutting, associate producer with Microsoft Games Studios, said players would notice a big difference from previous Halo titles.
"There is no Master Chief (the main character in previous Halo games), instead players are going to be more ordinary," he said.
There are a number of gameplay changes reflecting the fact players are now regular troopers, rather than the turbo-charged super-soldier Master Chief.
"This means they are going to take damage if they fall off buildings and aren't nearly as fast as Master Chief," said Mr Cutting.
The latest version of Halo has players in the role of regular soldiers.
Jon Hicks, editor of the UK's Official Xbox Magazine, told BBC News that the lack of Master Chief would not be a problem.
"There might be those who miss [him], but I'm expecting they'll be in the minority.
"Everything else is pure Halo - the weapons, the vehicles, the setting - and it's engineered into the existing world and storyline in a way that even the biggest fans will fully appreciate," he said.
Probably the most significant change is how characters' health is affected by events in the game.
While Master Chief regenerated health, providing he was not being shot at, the ODST squaddies have a limited supply, which can be topped up from only a few health packs scattered across the map.
The developers behind the Halo series, Bungie, have intentionally made the combat location - an African city called New Mombasa - a dark environment, so they have added a visor system that has night vision and identifies enemy troopers with a red outline.
As in previous versions, fallen enemy soldiers can be looted for weapons and ammo. It also sees the return of the silenced pistol that made its debut in the first Halo.
"The pistol is quite a throwback to the Halo 1 pistol, of which people were really big fans," said Mr Cutting.
The first in the series - Halo: Combat Evolved - was released on Xbox in 2001
The game is not just played through the eyes of a single ODST soldier. There are various items scattered throughout the game that belonged to fellow troopers.
Picking up the item will trigger a flashback, putting you in the combat boots of the lost teammate and allowing you to replay the events that lead up to the item being dropped.
"You find out what your team has been up to during the time you were unconscious after your crash landing on New Mombasa," said Mr Cutting.
The developers have also added a new mode to multiplayer called Firefight.
Entirely co-operative, the game sees up to four players defending themselves from successive waves of alien attackers, with each group being progressively harder than the last.
"You have to constantly adjust your strategy and work as a team, otherwise you won't last long," said Mr Cutting.
"As a co-operative game, its basically a score game and your team is trying to get the highest score possible.
Teams' scores are logged on a tournament ladder on the Bungie website.
Mr Hicks said the new Firefight feature gave the game a new dimension, compared with previous titles.
"Fighting off endless waves of enemies has been around since Space Invaders and given some excellent updates in Gears of War 2 and Call of Duty: World at War, but this adds a much brighter and more varied element to Halo.
"You really feel like you're facing a genuine threat, rather than a simple onrushing horde."
Mr Cutting said that the developers were now focusing all their attention on the next instalment of the Halo franchise - Halo Reach - due for release late next year.
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