Interesting...

I find the concept very interesting. However, I feel like it is missing a lot of things.
Like others said, it has untapped potential. I think it needs more upgrades (stronger link between the cars? Barriers that prevent the gold from falling off?).
I also think it needs some sort of change between the sceneries (one map snowy, another map rainy or sunny etc.).
The music was perfect and it really represents the whole idea.
Overall, think about what needs improving and build on it.

not bad.....

But this game is missing alot of elements that make people want to come back and play it again. First of it could use a story or maybe a character that drives the train, and then you could incorporate obstacles, different scenery, or have the player choose different towns to deliver gold to. Right now this game just needs a plot, thanks gl :D

Revise, Expand, Complete

This game has way too much untapped potential. The gameplay is solid... there's just little reason for me to want to continue playing it. The current result seems to be a beta test for a game that isn't yet done. I suggest adding story, extra features, etc. Also, add a visible form of locomotion; it's kinda bizarre seeing the trolleys trot along without a guide of any sort.

The gameplay is SOLID. Keep that in mind. Just try to flesh out the idea. You'll have yourself a classic in no time. Right now, though, this is just bare bones. Even Galaga and Space Invaders had a good story.