Fun game! Do the ores get better the deeper you go? I thought that at first, and then found a bunch of valuable ones near the start, though maybe that is just luck. If they don't they should, that would reward not blowing up.
Otherwise, I have a suggestion, could you either make menu and exit full screen be different buttons, or have a full screen button in a corner somewhere?
Finally, it would be less frustrating if rails could be retained when you blow up, even if you only keep half, or if they become more expensive, as they aren't very useful currently: due to the mines stopping the rails from being straight most of the time, they don't give that much of a speed increase, so it isn't really that useful.