This game is stuck in the development limbo known as Vaporware. Few to no details have been released about about its gameplay, plot, or release date since its announcement many years ago. It may or may not be in active development, but neither has it been cancelled officially.
This is a forthcoming standalone expansion for BLλCK MESA featuring the Xen chapters of Half-Life, redesigned and expanded.
Release date is not yet announced but it is speculated that the game will be released in 2013.