The concept is fun and very easy to understand. Had a good time planning my routes to optimize reward/danger. The reduced art style also matches the game very well.
I think the mechanics need some tweaks to make it a bit less frustrating, at the moment it feels unfair at times. My main issue is that enemies can spawn inside your train and spawning skulls fire the moment they show up. In these cases you just lose health without any possibility to avoid it. This could easily be addressed with a collision detection before spawning enemies and a timed delay for the shooting.
