The digital-heavy campaign rolled out last week, inviting customers to guess the mystery flavour at the iD3 microsite for a chance to win £20,000.
Xbox 360's and gig tickets for O2 shows are also up for grabs.
Creative agencies rehabstudio and Initials Marketing developed a three-part episodic 'choose your own adventure' game, which pits the user deep in London's grimy underworld, where they must unlock the secret flavour in a case of mistaken identity.
Digital planning was provided by AMV BBDO London, while Upset TV wrote, directed and created the game.
The game blends live action footage with 3D interaction, sound recognition, interactive scenes, and film content giving the experience of a professional cinematic production.
To play the game, customers must insert a p
romotional code found on the inside of the iD3 bag, which gives the user six "lives".
The advergame is integrated with Facebook Connect, which enables a personalised experience for Doritos fans by inserting content from their Facebook profiles into the film.
Where most applications of the Facebook Connect technology use it simply to populate a profile, iD3 uses it to personalise the narrative and extend the game from the website into Facebook.
Support for the campaign has been shrouded in mystery - with grassroots seeding and an exclusive blogger outreach programme.
A live Twitter feed and Facebook fan page will keep Doritos fans up-to-date with the adventure.
The campaign has only recently launched, and yet Doritos iD3 is already gaining attention on blogs, forums, reviews and Twitter. There is high engagement on the brands Facebook fan page, with hundreds of fans guessing the mystery flavour.
Tim Rodgers, rehabstudio's creative director, said: "We had a challenging brief to extend the plot and interactivity beyond the video.
"The 3D scenes we're creating for the game give the user full control to explore and move the story on. Plus we;ve created a number of secret levels and experiences for hardcore gamers. iD3 is the perfect showcase for our creative and technology skills."
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