More fun than it looks at first glance. Nice background music choice. I found this game stressful and relaxing at the same time. Great job! I don't know if I failed or completed level two because the timer ran out right when I was dropping a crate and I happened to be over the quit button so I accidentally clicked that. So having a slight pause between the timer running out and the score showing up would help. Or prevent the button click for a short period. I would like to have seen the other levels but I see you mention there is a bug getting to level 3 anyways.
For future levels and difficulty it would be cool if different colored trains could appear on different tracks. At least on the first two levels the trains were always in the same position.