Xash3D engine is an open source remake Goldsrc engine and can run most of the game, or module, such as Half-Life body and the revised CS and the like.
Install the application
Half Life copy of the relevant documents, from steamapps / common PC on / half-life / valve copied to / sdcard phone / xash / valve
Download version 0.16 of additional file and extract the files inside the folder to above to start the game.
Xash3D engine is the developer version of Android device adaptation, optimization level is very good.