GameSpy asks Jess Cliffe, co-creator of Counter-Strike for the Xbox, about the game, translating the gameplay to the Xbox, and lack of single-player missions:
GameSpy: The purchase interface in the Xbox versions is quite different than what CS fans may be used to. Can you briefly describe how it functions and why it was changed?
JC: The pie-buy menu system works better with the thumbsticks, so we decided to go with that rather than the Windows-like menu system in the PC version. We've also simplified the categories so you can browse through the menus quicker and get to the action. In CSX you'll spend less time thinking about what and where to buy, and more time making your foe look silly.
News source: VE3D