Your game looks amazing and I like the concept! Something I struggled with was the urgency of the game. I found that the most efficient way to play was to just put it on the lowest speed and wait, which is kinda boring and it made the loop feel long. I would also suggest to make it a bit more clear that you can upgrade your train so you can add more wagons. Maybe add the train upgrade to the same place where you unlock the wagons. Overal Great job!