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Long-awaited real-time strategy game (RTS) StarCraft II: Wings of Liberty has gone on sale after a 12-year wait.

The game follows on from the 1998 release of StarCraft, putting the player in command of a group of humans battling for survival against an insect horde and telepathic aliens.

The title has been created by US developer Blizzard, the firm behind the popular game World of Warcraft.

StarCraft II now holds the record for the longest time before a sequel.

The first edition sold over nine million copies and is seen as one of the defining games of the genre, along with EA's Command & Conquer.

It took the classic RTS premise of "manage your resources, build your army and defeat your opponent" and turned it from a two-way fight into a three-way melee.

The recipe was an instant hit with gamers, spawning three major add-on packs and having a knock-on effect in the real world.

In 2005, South Korean fans watched the final of a proleague event while University of California, Berkeley, offered a course on the game, that explored "various aspects of the game, from the viewpoint of pure theory to the more computational aspects of how exactly battles are conducted".

The new game, which went on sale at midnight on 27 July 2010, stays close to the original.

Throughout the seven year development period, designers have stuck with the three races - the powerful Protoss equipped with telepathic powers, the insectoid Zerg who can swarm defenders by sheer weight of numbers, and adaptable Terrans who can steal technology from the other two races and modify it to their own ends.

That said, Blizzard has made changes in the way units are upgraded and altered and improved the way they interact with the in game environments.

Speaking to ´óÏó´«Ã½ News, Blizzard's director for internatinal operations Michael Ruder, explained why it had waited 12 years to release a follow up.

"Late is a relative term, because we don't consider it late, because our time line is undefined," he said.

"When we started the process of developing StarCraft II, we had aspirations about what we wanted that game to be.

"But in the middle of that process, in 2004, we launched World of Warcraft and that was a little bit surprising to us in terms of how big that became.

"When we launched World of Warcraft we had a few hundred people, now we've got over 4,600 people so that's put quite a bit of a priority into the company in terms of dealing with that success," he added.

Unusually for a video game release, there have been no reviews before it went on sale.

It is thought that the firms Battle.net services are so locked into the game, that it was not possible for the media to review it before the servers went live.

In March, the games lead designer, Dustin Browder, told that a patch would be released within a day or two of the game going on sale.

"We will have a day one patch, a required day one patch," he said, which will allow the Battle.net team "a little bit more time to sort of get their ducks in a row".

You can hear the full interview of Michael Ruder talking about StarCraft II: Wings of Liberty with Adam Rosser in the next edition of 'Game On' this Saturday during Up All Night on ´óÏó´«Ã½ Radio 5 live.