Gordon Freeman, protagonist, HEV suit, crowbar, action pose, fighting headcrabs, dystopian City 17, Combine soldiers, alien creatures, Xen, dark corridors, Black Mesa Research Facility, physics-based puzzles, atmospheric lighting, first-person perspective, detailed textures, industrial structures, sci-fi weaponry, immersive environment, dynamic shadows, 3D composition, realistic materials, Valve's Source engine aesthetics, iconic orange and black color scheme, hazard stripes, emergency lighting, ominous ambiance.