This would be a perfect demo for black mesa, it shows the contrast beetween action and exploration.

It would be nice to see more levels, even link them as a mini chapter, about the same lenth as surface tension. When the tram leaves to the next section it could lead to a flooded part of the base where the tram takes a plung into Ichthyosaur infested waters if the players does not jump off in time, just a thought.

Pros - Good attention to detail
Level design
Fun gameplay but not over the top.

Cons - The fact you play as gordon takes away from the continuity of the original storyline, reskin player as security guard/scientist ?
Rockets need to be placed about rather than the box
Could do with a few more grunts when you turn the tram line back on

Other than that spot on !