This is great. I really like the reverse tower defense schtick. I also really liked unlocking the additional routes by blowing up the icebergs.
When I got a longer train I really wanted a "repair all" button. I would also have liked to be able to reorder the cars. It felt like the balance was a bit off, I don't think there was any reason to buy anything but the drone launchers and maybe the area effect fire after the first loop.