Sequels are big business in the games industry. Once a studio hits on a successful idea, there's often a lot of pressure from publishers to continue the winning formula. And while some people like to bring out a sequel every year, others spend an age getting just one ready. Rare have spent five and a half years on the sequel to Perfect Dark on the N64. Itself a spiritual sequel to the dearly beloved Goldeneye, Perfect Dark won the hearts of hardened 'Goldenistas' with hugely customisable multiplayer modes and a fun story mode that even supported two player co-operative play.Since then, a sequel has been slated for GameCube; then - following the Microsoft buy-out - for Xbox. With the perfectionists at Rare unable to keep their hands off it, it slipped again to Xbox 360. But perhaps this is a blessing, and Perfect Dark Zero standing proudly shoulder to shoulder with its comrades in the Xbox 360 launch line-up is a stirring sight.The story once again concerns itself with the adventures o