Black Mesa is a fan-made remake of the original Half-Life, the seminal first-person shooter from 1998. Originally released as a free mod with a missing ending, it was later finished and released as a commercial game, with the blessing of the original developer (and creators of the Steam platform), Valve.
Though I have played the original Half-Life, it's been several years. Playing Black Mesa is very familiar, despite significant improvements, upgrades and changes.
At this time, The Dandroid has 36 views for Black Mesa spread across 10 videos. The game makes up 20 hours of published video on his channel, roughly 2.26% of Black Mesa content that The Dandroid has uploaded to YouTube.