Play as a scientist in the depths of Black-Mesa after the resonance cascade struck the facility. Fight through waves of U-S special forces and aliens from the Xen border world in a more scifi and vibrant Black-Mesa.
The HECU deployed in the Depths have locked up most blast/fire doors to halt the alien assault. To progress to the storage areas, these blast doors need to be opened, despite the threat of the aliens.
Also sorry for the overload of yellow/orange lights. There are plenty of other coloured lights in the map so don't worry.