Really well balanced, really fun to play, really good game! I did find two bugs though.
1) When selling a coal burner, the tiles it unfreezes stay unfrozen and you keep losing coal because of it
2) Enemies are attacking coal burners during their death animation
Other than that though, I had a lot of fun with this game. One of my favorites of the jam so far. Keep it up! If you guys could also play and rate my game as well that would be great.