This virtual world includes activities like Starfighter races, droid puzzles and tower defense mini-games.

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Yesterday, PopCap announced a sequel to its insanely popular tower defense game Plants vs.

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When U.K.-based developer Paul Preece built a Flash game called "Desktop Tower Defense, " he added a snippet of Mochi code.

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Every time someone plays "Desktop Tower Defense, " no matter where it is on the Web, they see an in-game ad and Preece snags a 50% cut of the generated revenue.

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The largest and most well-known is Al Jahili, which was built by Sheikh Zayed the First in 1898 as a defense tower and a summer retreat.

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The third tower was occupied by the Secret Service, the CIA, the Department of Defense and the Office of Emergency Management, which would co-ordinate any response to a disaster or a terrorist attack.

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