You could tell someone that this was an official expansion to HL2 and, as long as they don't look too hard, they'd believe you.

The newer weapons feel satisfying and creative to use to the point of one being just a general problem solver, the voice acting is good enough to fool anyone to believe this is a professional project, and the story is deep enough that there are entire branches dependent on a side character you can ignore soon after meeting.

The only gripes I can think of after playing is that there were occasional bugs with sprinting and some segments dragged on too long, but I can consider them nitpicks. The fact that this was made for free is astounding.