I like how you implemented the map! The overall mechanic of the game was interesting, though it wasn't quite challenging enough to be a "puzzle". I don't know if you wanted to make it a puzzle, or just a journey, but it's something to think about. As for a journey, I think you succeeded, and you could even build more on that story in future versions!
I liked that you put thought into the mood, as the movement and guard patrols weren't complex or challenging. Maybe you could have the trains operate on their own kind of schedule, like real trains do, so you have to try and catch the one you want before it departs! Again, it depends on what kind of game you wanted to make :) I had fun playing yours!