Very beautiful, a really interesting idea mechanically. Unfortunately, I feel I wasn't really incentivized to engage with the mechanics, I hardly ever used the dice modifiers because it felt like I could get away with blasting just through my dice - this was my undoing however, as I did eventually run out and got roasted to a crisp.
Perhaps if there was more information about how often the dice would be spawning, as well as maybe a bar that displays what speed the train is at that you have to keep filled, that tension would be more present and force me into thinking more carefully about how I used my dice.
Still, I really like the core idea here, and I think it ties in so well with the narrative. Great work!