This is a source interpretation of gt_m1_exp based on the original by you-tuber "LambdaGeneration". In addition to reworked lighting (he'd mentioned he has unhappy with how saturated it originally was), there are some general changed including an expanded layout(See: capture 2), physics, improved path-finding (you can take the scientist between both ends of the map)(See: capture 4), as well as a secret challenge mode (See: capture 3).
Has anyone tried remaking the hl1 layouts in black mesa?