Half-Life: Opposing Force Xash3D FWGS engine (typically for Android or remastered PC setups), you must transfer the official game files from a licensed installation into the Xash3D directory. 1. Preparation & Requirements Legal Copy : You must own and have installed the Steam version of Half-Life Opposing Force expansion Xash3D Launcher : Download the Xash3D FWGS app from the Google Play Store or GitHub.