Never got around to playing Half-Life 1 to completion, but played Half-Life 2 the day it released and it was my favourite game for the longest time. Playing through Black Mesa gave me a lot of the same vibes and I was genuinely surprised it's as long as it is [the story is about as long as HL2 + Ep1 & 2]. The puzzles are also more mind-bending than it's sequel. The art-style and sound/music are absolutely spot-on. Seriously, if you're into shooters in any way shape or form, you're doing yourself a disservice by not playing this!

The only gripe I have is that in some places there is no clear way forward, but I think this is down to the original game's age and design philosophies back then [remembering this is essentially a remaster of a 20+ year-old game!]

All-in-all, I cannot recommend it enough.