The Vanishing Point competition is a viral marketing campaign organised by 42Entertainment, which ran the ilovebees.com promotion for Halo 2.
The campaign has seen wooden puzzle boxes containing USB keys delivered to media outlets taking part.
"The Vanishing Point sweepstakes is a large-scale online and offline collaborative puzzle game," said Microsoft in a statement.
"Vanishing Point takes online games to new heights with tough challenges, big rewards and events scheduled around the globe. Players worldwide have already created forums and wikis, and posted thousands of messages online."
The game is being run by a puzzle master called 'Loki' and is "ridiculously hard", according to the website.
The first clue will be revealed at the Consumer Electronics Show at 18.30 PST and further clues will be posted on YouTube and on media outlets.
Other prizes include AMD hardware, Microsoft software, and Xbox 360 games consoles, but the top prize is a flight in low earth orbit with Rocketplane Limited.
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