Really amazing visuals and polishing! the change of the map as I mine was a really nice visual addition. The gameplay mechanic is outstanding for 3 hours only. The game feels well balanced with really nice mechanics.
Really nothing to complain about! The only really small change I would suggest is that instead of having each coal shown, you could add a menu to show the amount of coals since it is a bit hard to see when I am under coal dust. Nonetheless, it is a great execution of an amazing concept!
Great job!