Spirit of Half-Life (SoHL) is a modified game engine for Half-Life 1 modders that includes many new things not seen in the original Half-Life engine by Valve. This includes reflections, mirrors better lighting, weather like moving clouds, rain, snow, and fog. Physics capabilities like picking up objects and dropping them, or when some thing explodes objects go flying off in the direction.
The glass only reflects the NPC,the player and other things.But there is a room on the other side of the glass.HLFX makes real life mirrors.If you have seen the shiny cube demo,you will know what I mean.