The game looks great! I really like the concept, I just feel like you didn't push it far enough. Like, most of the time I didn't have a need to deattach from the train. So, most of the time I spent attached to Rapidfire, firing enemies like a turret without even moving. If only there was a real need to deattach, like to pick up a repair kit or a shield for your train or a powerup. And another thing is that near the end the amount of enemies if way too much, in my opinion)
I really think you should continue developing this game after the jam ends. It has so much potential, hell, I would even consider buying it. For me it feels like a nice twist on a TD genre, where you're defending a moving objective. It can even be a roguelite, where every run is unique by collecting some random powerups and going through different bioms. I mean, there are so much possibilities with this game )